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!