I put this here hoping for more exposure then it might get in the street rod section.
This is pretty long, please read the whole deal, I tried to answer all the questions up front.
The truck does not appear to be over heating, the whole deal only happened after the truck has gotten to operating temp and is shut off.

My 49 Dodge truck has a complete stock 96 Dakota chassis and 5.2 drive train on a stock (other then a wheel base shortening) Dakota 4x4 chassis. This was all factory stuff out of a 44K miles Dakota that rotted away.

The 49 sheet metal sits pretty low on the Dakota chassis, there is only about 4" of clearance above the factory air filter housing and the hood center. This created an issue with the factory radiator housing concerning the hood side clearances. I had to modify how the top of the radiator was held in place, but it worked with the stock Dakota aluminum & plastic radiator. Space under that hood is at a premium, I had to replace the original Dakota overflow bottle with a much smaller cheap plastic one. I don't believe that smaller overflow bottle was big enough. After a run and a stop, that overflow bottle would fill and spit out a bit of coolant, then when it cooled, it would suck it back into the radiator. every time it would spit out a bit more, until the bottle was empty. About once a month the coolant level in the radiator would be below the radiator cap level (very hard to check because the radiator cap was up under a section of the hood that does not open.

The OEM aluminum /plastic radiator started leaking at the tank/core seem. I replaced it with an aluminum crossflow with an electric cooling fan that fit in the hole much better. Its a slightly smaller core then the OEM, but it is a 4 core rather then the 2 core OEM. This radiator is suppose to cool 450HP, that 5.2 isn't anywhere near that HP. The top of this radiator is several inches below the highest point to the cooling system (where the upper radiator hose goes over top of the AC compressor, the AC does not yet function). I've added an in hose radiator cap into the highest point in the upper hose as an attempt to keep the cooling system full and I relocated the over flow hoses to the top cap. Using the same overflow small tank in the same location about even with the top of the radiator, I experienced the same coolant loss as I did with the OEM radiator, but at least I could top off the radiator easier. I was adding about a 1/2 quart a month, it was always over flowing and dumping it on the ground after the truck was shut off. The cooing fan functions, but rarely runs, When it does run, it brings the coolant temp down quickly and only runs a few seconds and shuts off. The factory gauge does not show it running hot. .

I've replaced that overflow tank with a better tank (but not much larger) in a position that is even with the in hose radiator cap, that new tank is only a 1 liter tank. No larger tanks will fit under my hood, but there is enough space I can add anther 1 liter tank along side of the one I have. If I add a 2nd tank, and plumb both together, do you think I will solve my over flow problem?
Pictures, 1 & 2 the OEM vertical flow on the bottom and the new aluminum radiator on top, see the difference, the OEM is a 2 core, the Aluminum is a 4 core.
pic 3, Current recovery tank with the hose mounted in line cap, and how it looks under that hood. Space is a premium.

Look at the reservoir that the Dakota had and compare the two. I have 96 ram so i think they are about the same cooling wise. My reservoir i believe will normally hold about a half a gallon of coolant and the other half is for expansion. That tank you have is not anywhere close to it so i can see why it's a problem. Again i didn't measure how much it holds so i am guesstimating. But i would look for a reservoir somewhere similar in size. That tank doesn't have enough room. Here is what a 96 Dakota has according to google.

See, that is the problem, I can't find any numbers telling what the capacity of the Dakota original recovery tank was. From what I have been able to gather, the Dakota OEM recovery tank appears to be in the 2 liter range. The problem with larger tanks larger then the aluminum tank I have is their height. There is no place under the hood of this truck that a tall tank would fit. Every recovery tank I've found that has more capacity then this aluminum tank I have are all too tall. I've looked at hundreds of them.

I believe I have enough space to add another one of these aluminum tanks along side of the 1st one The 1st tank is attached to the air cleaner housing, I believe I can put another tank like this one towards the front of the other tank also attached to the air cleaner housing, the oil fill location is the problem area with that. If I can make it fit, I could connect the two aluminum tanks together and and use them like one tank, and in theory double my recovery tank capacity. Which I am assuming would solve my problem. That is the only solution I can see.

At this point, I'm doubting my own thought process, which is why I'm turning to you guys. Any thoughts are welcome!

What about a 78-79 Dodge or Ramcharger overflow tank? Could you make it fit?

This came to mind also. You would have to make a bracket to hold it but looks like it would fit above the radiator. What about in front of the radiator off to the side? Any room there?
If you are not familial with the above tanks here is one.

I have an old one of these late 70s Dodge truck recovery tanks here. If it didn't have the mounting tabs as part of the tank, I could put it above the radiator. The mounting tabs want to occupy the same area as the AC compressor and the serpentine belt, it doesn't fit between the hood and the motor. if I could turn it on its side, it would fit into the hole, but then the fill cap is under the part of the hood that doesn't open, and it would only have about 1/2 of its capacity. Even if it could work sitting on its side, I think its too long to clear the closed hood wings.

Pics attached. The above 70s Dodge tank above the radiator, and with a tape measure showing the space I have. The shortest larger recovery tank I've found is 10" high.
The aluminum tank is 6 1/2" high and 4 1/2"" wide. It would fit at the very center under the part of the hood that doesn't open, but that wouldn't help much because I still couldn't add anything to it, and its still too small.

I suppose I could mount another tank like the one I already have as a secondary over flow, kind of like a recovery tank for the recovery tank, but then I would have a big batch of 3/8" coolant recovery hoses running all over the place because the radiator cap would be between the two recovery tanks. How would I run the hoses to them?

For reference,
The 2 pics with the truck in red primer show the OEM Dakota radiator mounted in the truck. The both top corners of that radiator barely cleared the hood sides when they were closed. By barely, it means I couldn't get my little pinky finger between the hood and the radiator. These pictures also show how the hood opens with the center part not opening. The corners on the hood near the edges of the radiator are curved in 2 directions, side to side, and back to front.

The two pic with the truck painted blue show that 70s recovery tank sitting in the hole upright. If it was turned on its side it was taller. The pictures are not at the same angle, but close enough to see the problem.

I think the best bet is to fabricate something that will fit above the radiator. That seems the only space you have.

Well Gene, if nothing else, your under hood looks more organized and cleaned up than a lot of chassis swaps I've seen. Your issues has me planning ahead to probably locate my battery somewhere other than under the hood when I build my 56 on my 2001 Dak chassis. Is the battery in your 54 remote located or in the box under the cab floor? I ask because I see the pos/neg posts under the RS hood section in your 54. My 56 will likely use a remanned 4.7HO engine which I think is smaller than the 5.2V8 or the 5.7V8 Hemi. On my 2001 Dak the coolant surge tank is built into the radiator shroud with the 4.7V8. Hopefully that will fit under the fenders and hood of the 56 rather than trying to use the 56 radiator. I can modify the original 56 radiator mount frame as needed if the 2001 Dak radiator/surge tank is comparable in size to the original radiator in my 56 which has the Poly V8 in it now. Also, with the 4.7V8 the radiator/surge tank/shroud/thermostat is all located to be accessible under the DS hood section, nothing would be under the center stationary section of the hood.

Also, since I want to use my 56/Dak as a daily driver I plan to locate the battery and fuel tank somewhere back in the chassis to get more weight over the rear axle. Like a fuel tank in the frame behind the rear axle, battery in a frame mounted marine plastic box, with jumper lugs under the hood and a battery tender hookup somewhere between the cab and box on the DS.

Andy, the under hood of my 49 looks more organized then most chassis swaps because I've had more experience dealing with this era Dodge trucks. That translates into "I've messed this up more times the most others have attempted this."

The battery in my 49 is in the left front corner of the bed. The fuel tank is in the factory Dakota location, which puts the gas fill tube right behind the battery box, it that left front corner. I've added a fill door into the bed side. The bed floor on the step side beds sits a couple inches above the frame rails on the Dakota frame between the top of the frame and the bed floor. This means there is not enough space between the bed floor and the frame for a battery. Even the low frame area in front of the frame kick up that is just behind the cab isn't high enough to put a standard height car battery. The outside bed wall is also just a few inches on the outside of the frame, so there is no space between the bed side and the frame to place a battery. That would mean the battery would have to be placed inside the frame rail. On my truck, withy the fuel tank occupying the space inside the frame rail on the driver side of the truck, the battery would have to be on the passenger side. The thought of climbing under the truck to get at the battery wasn't something I was very interested in doing. Giving up a 1" wide x 12" long piece of bed floor space was an easy decision.

The battery on my 54 sat under the top of the fender. That area on these trucks with the wide front fenders is pretty much dead space. The emissions carbon canister sits in that dead space under the right side fender on my 49, but that dead space is unoccupied on the left side. With the battery under the fender, you need to be sure you have the space to pull it out from under the fender should it ever need service. I can tell you that lifting a car battery out from under the fender, and then having to lift it over the fender once the cables have been disconnected is not fun. Enough not fun that the battery in thr bed was much more appealing for this old man.

I'm not so sure the 4.7 has a smaller footprint then a 5.2. It has less cubic inches, but I'm not sold on the idea the outside dimensions are smaller. Those valve covers on a 4.7 are big. The 5.7 has a bigger foot print for sure.

The 49-60 Dodge trucks have a lot of space under the hoods, side to side. The problem is, a large part of that space is under the fenders in areas that do not have easy access. I could probably put a 2" cube in the dead space area under my driver side front fender, but gaining access to what ever is put there is very hard. Everything that is under the hood that you want easy access to hangs along the hood lines on the fenders edge and blocks the access to the area under the fenders. I could put my overflow tank under the front fender, but then I couldn't see it, I couldn't fill it, and I could barely reach it, and that was before all the other stuff got hung in the way.

My 49 has the body channeled over the frame, its something that just happens when you use a Dakota frame, the old frames sat higher then a Dakota frame and the old cabs were taller between the floor that sat on top of the frame, and the bottom of the doors that often extended a few inches below the frame. With my 49 being a 4x4, that just compounds the challenges.

As far as my coolant recovery tank issue, I have decided to order another aluminum recovery tank like the one I have. I was checking the truck over this afternoon. In the past 2 weeks we have put nearly 400 miles on the truck. The coolant level in the radiator cap in the upper hose has the level about a 1/4" below the rubber seal. The current recovery tank has a sight tube on the one side. You can clearly see where the level has been in that tube recently, at just over 1/2 way up. Currently the bottom of the recovery tank has some antifreeze in it, but it does not show up in the sight tube. If I topped off the hose filler, and added enough to show about a 1/2" on the lower part of the sight tube, with the system cold, I think it would only take about a cup of antifreeze, but if I added that much, in a couple weeks I would be right where I am now. .
Last week we had near 80 degrees a coupler days and we drove the truck over 200 miles, so the system got a workout.

I believe if I add the 2nd tank, and use it as an overflow for the 1st tank, I should be able to top off my cooling system and add about an inch to the bottom of recovery tank #1 so I can see it in the sight tube. Then connect the overflow tube to the bottom of tank #2 (leaving it empty) with the coolant dump coming out the top of that tank, I believe I shouldn't loose any coolant, and I should be able to maintain the coolant level in tank #1 within the sight tube. Am I thinking this right?

I'm trying to avoid making a recovery tank. At this point it would have to be made out of steal, not something I really want a coolant recovery tank made out of. Gene

If you add another tank just put a "T" between the two so it will fill both of them rather than have a "over flow" tank. If air can in the cap it won't pull coolant back it will be replaced with air. Just make sure the two tanks are parallel, leval (one not higher than the other) if not one will collect more than the other.

That underhood is tighter than expected. Hmmm....lots of good ideas in here. Just as a side I think the 4.7L is wider than the 5.2 or 5.9 Magnum engines.

For certain the 4.7 is wider across the valve covers than the 5.2 and 5.7. Those SOHC heads sit wider and spread open more over the block-V and higher because the cams are up there too. Now, as long as I plan clearance over the valve covers I'd have no issues accessing them. But the 4.7 has hyd lifters I should rarely if ever need to get in there. When I use the remanned 4.7HO engine it'll have stronger valve springs, better head gaskets, improved lifters, improved oil flow (especially to the lifters) which addresses all the known issues with the older 4.7. I plan to use the compete cooling system from my 2001 Dak which includes the coolant recovery tank on the fan shroud, and a high flow electric fan in place of the stock hyd drive fan.

I've been using an electric fan on my 2001 Dak since I bought it used back in 2011, and never had an overheating issue. Which is likely a good reason why my Dak has achieved 203,000 miles and is still running good. So given that, an updated/improved 4.7HO remanned engine should be reliable for many years to come.

Vintage bladder bag?

First off, I love your truck!!

Your idea of mounting a second tank beside your current overflow tank will be the easiest. If that does not work out, perhaps one of the following ideas will be helpful.

Is there space to mount a recovery tank on the firewall? I'm thinking of something similar to the 1970's truck tank at the top of the firewall just under the hood. The mounts may need to be designed so the tank is easily removed to provide access to the distributor.

Does the entire recovery tank need to be above the radiator? I thought only the top of the recovery tank or the fill point needed to be that high. If so, could you mount the overflow tank under the fender where you have space, but can not access it easily. Then run a pipe or hose up to the firewall or some other location so it will be up high enough? This is assuming you can mount the recovery tank in a location where it can be seen under the fender, even it you can not reach it, so you can tell how much coolant is in the tank. Perhaps you could look in over top of the front wheel to see the tank? A tank is this location would need to be made out of something strong so stuff kicked up by the front wheel will not rupture the tank.

Taking care of all the little issues after a non-factory engine swap can be time consuming. My father performed many such swaps. Sometimes the smallest problems can really test a guy's persistence!

I do appreciate the responses. They give me food for thought. Its difficult to show how tight everything is stuffed under that hood. With pictures you loose perspective, both space and objects appear larger, and sometimes smaller then they are. Without a reference, its pretty hard to really judge the space.
I dug through some of the inbuild pictures of this truck, some of them may help.
QuickDodge,
Picture 1) shows the top of the firewall without the hood in the way. This is just before the removal of the old radiator. It was higher then the current radiator so the radiator hose connection is lower, but the top of the radiator hose remains that high where it goes over the top of the AC compressor (typical 5.2/5.9 Magnum upper hose routing). The two nut clips and the metal they are connected to at the bottom of the picture are still present. The hood center bolts to these two nut clips and also bolts at the top of the firewall near the wiper posts. The highest point on the red primed firewall is about 4" above the the top of the air filter housing.
Picture 2 is with the old radiator removed. I've added the in hose radiator cap into the upper radiator hose. it is the highest point in the cooling system, and where I have the current recovery system operating through. Two things to notice here, the curved bracket above the brake booster is the hood open support brace. That brace is two pieces, the straight piece at the rear of it connects to the under hood bracket and when attached, would be very near the top of the firewall/cowl. The 2nd thing to notice is the the top edge of the fender on the right side of the picture. It shows how much stuff is hanging on that fender edge. The only possible opening is in the lower right corner. What is not bolted to the fender in that area is the hood latch hook. With the hood latch hook bolted in place, I can not get my hand through that area.
Picture 3) this is the current recovery system. The overflow hose from the in radiator hose pressure cap travels under the radiator hose and is zip tied to the heater hose before it swings up to the bottom of the aluminum recovery tank. The gate valve in the heater hose it to shut the coolant flow off to the heater core through the summer. in this picture the valve is open. The top of the recovery tank is about an inch above the in hose radiator cap, and that cap is 16lbs (the only pressure they make for those small caps I'm told). The over flow for the aluminum tank comes out of the highest connection on that tank, and it goes over to the radiator hose, and is zip tied to it until it attaches to a metal tube that drops down to under the truck to dump. One thing to notice here, near the overflow dump tube you can see the hood latch hook bolted in place. For reference, that hook is 3" from where it bolts to the fender to the top of the hook, and the hook itself is 2" wide. The only open area along that fender edge is where the metal overflow tube turns down. That dump tube sits just inside of the frame rail, and from the top of the frame to the top of the fender is about 11".

I'm believing at this point that my aluminum recovery tank is about an 8oz cup short of having enough capacity. The system appears to maintain the coolant level at about 1/2 the diameter of the 6" long high arch of the upper radiator hose, but the recovery tank is empty. I don't like the idea that I need to take the radiator cap of to see the coolant level in a recovery system.

The possibility of putting an overflow tank in the location of the dump tube does exist. I can get an overflow tube tank that might fit in that area. Those tanks have an inlet tube that goes within an inch of the bottom, and a dump connector that only goes about an inch from the top. They have a cap on them, but it would have to tuck under the fender and that cap would be inaccessible. If I filled my aluminum recovery tank about an inch from the bottom so it would show in its sight glass when cold, then run the aluminum tank overflow into the inlet on the tube tank, then just dumped the overflow from the tube, would that maintain the level in the aluminum tank? My thought is that when the aluminum tank over flows, it would overflow into the tube, and when it cooled, it would suck the coolant back into the aluminum tank. I would probably have to maintain enough coolant in the tube to cover the bottom of the inlet tube. In my mind that would probably increase the capacity enough to maintain the correct coolant level in the aluminum tank.

I also think I'm going to lower the temp at which the radiator cooling fan comes on (it is adjustable). The truck does not appear to over heat, the fan only comes on when I hit stop and go traffic after a highway run. but maybe if the can kicks on a bit sooner, that might help. I had to remove the mechanical fan for radiator clearance.

There has also been a few questions about putting things under the fenders. Again, some old build pictures may help answer some of those questions.
Pic 1) this is when I was building the inner fenders. This is the passenger side with the inner part of the inner fender bolted to the truck. The completed version had those inner fenders extended outward, and was level with the arch of the inner fender to cover the tires and connect to the outer fender sheet metal.

For reference, the bottom edge of the small square piece in front of the door is the level of the top of the fender. The front nose panel is bolted in place at its current position. The top curve of the fender runs in a straight line from the bottom of the small square to the top of the nose panel. About even with the front of the tire you can see the bracket bolted to the inner fender. That bracket holds the 4" diameter plastic carbon canister that is still present on the truck. The carbon canister is about 8" long, and the bracket captures the center of the canister. The area where the inner fender curves forward and is bolted to the nose panel is the only unoccupied area under the fender, as you can imagine, getting into that area is not simple.

Pic 2) this is the driver side inner fender. The angle iron here is holding the nose panel in position and the rear is clamped to the fender mount. If that rear clamp was up 2" higher, so the bottom was under the square piece in front of the door, the top of the curved edge of the outer fender would be under the flat part of the angle. For reference, that piece of tubing that is clamped between the angle and the inner fender is 1 1/2" high.

Pic 3) This is with the outer fender bolted in place. notice how congested everything is? The ball looking thing is the cruise control servo. What you can't see is that towards the front of the servo, tucked under the fender is the ECM and its associated wiring and behind the rear of the servo is the heater fan relay, also tucked under the fender.

The last post already showed the driver side fender.

I have a 52 Dodge with a 330 Desoto Hemi. Runs on a Dakota clip. I run an old metal canteen. Seems to do the job.

Have you considered that you might be overfilling the system? I had a similar issue because I was filling an a/m aluminum rad all the way up to the fill neck. Now I just fill to cover the cooling tubes leaving an inch or so down from the top. No more problems.

Look at the pictures.
The top of the aluminum radiator is at least 6" below the top radiator hose, I'm not sure the top of the radiator is even above the thermostat in relation to the ground. Even the original Dakota radiator was lower then the top radiator hose, but it only cleared the hood after the top radiator mounting system was removed. I replaced the original radiator when the seal between the aluminum core and the plastic tanks started leaking. Any Dakota replacement radiator would have had to be modified to fit into this truck.

The closed system is pretty much a requirement if any coolant was going to be in the top radiator hose. The current recovery system maintains the coolant level, but it runs below the built in sight tube on the recovery tank. If I add just a bit more to bring it up to just above the bottom of the sight tube, it will blow the extra out. The desire is to have the level at a point where I can do a quick visual check and determine if its full or not. I believe the current 1 liter aluminum over flow tank is probably just about an 8oz cup too small to have the level where it can be seen at a glance.

i am looking for a way to increase the recovery tank size on a truck with very little available space, and most currently available recovery tanks or bottles, or tubes won't fit anywhere on this truck and be easily visible.

Since this thread has been started, I have lowered the temps the electric fan comes on, thinking it was possibly set too high (it is adjustable). At this point the cooling fan comes on just before the thermostat opens, at around 180 degrees (has a 195 stat, truck gets driven in the winter, I'm not lowering that stat temp). Before the fan was set to come on around 210 degrees. It seems to have helped a bit, at least the under hood temps seem to be a bit cooler, but the fan runs nearly all the time the motor is running. When the fan temp was higher, the truck didn't seem to overheat unless it was shut off and then restarted. The fan ran a minute or two and the temp was back into the normal range. The weather has been so up and down the last month, I really can't get a handle on if the change in the fan turn on temp has made much difference.
That said, the over flow tank issue is still the same.

I think the next step is going to be to install an over flow/recovery tube into the dump tube on the current system and then raise the coolant level up just above the sight glass (about an inch off the bottom of that recovery tank) on the current aluminum tank. I won't have any access to that extra recovery tube, but if it will maintain the level in the sight tube on the current tank, I'll consider that a win.

Currently, some other things have taken a higher priority with the truck. I've gotten the custom fabricated soft bed cover made and installed, and I'm working on making real door panels. That stuff sucks up money FAST!