looks to me your plan will work as you think it will.
i'll also bet the truck may have a better ride, as the current bars are acting like they keep getting softer and softer, causing you to keep adjusting the bars, and i wonder if the current bars are getting close to failure/breaking ?

I suspect the current bars are getting closer to failure every day, but I'm not too concerned about them breaking. The bars appear to be loosing their spring tension. When I started out, that adjusting bolt had more then 1/2 of those threads in between the anchor and the key instead of being above the anchor like they are now. Its taken 3 summers and 2 winters (about 20,000 miles) to get to this point.

Weak torsion bars are sort of like weak coil springs (except you can't adjust the weal coil springs like you can torsion bars). They just keep sagging until the springs fail and the truck rides on the bump stops (or the coil springs bind up the coils against each other and the truck rides on the bump stops). Weak torsion bars don't usually break, they just don't support anything. Its kind of a slow ride down to the bump stops instead of a fast drop like a broken bar would do.

The biggest issue is, I suspect the weight on the current bars is more then they were designed to carry, but I have no ides how much too much weight is there. Other then about 15" being docked off both the front and the rear of the frame, everything on the Dakota frame is using factory mounting. The radiator, the motor, trans, transfer case, all the front and rear suspension, front and rear axles, and even the fuel tank and exhaust, are in the same place Dodge put them on this 4x4 frame at the factory.

The only difference is the sheet metal, glass, and interior of the cabs. Even the cab firewalls are in the same location (except maybe the old cab is an inch more forward). The problem is, the old cab glass and roof are closer to the firewall then the Dakota glass and roof are to the Dakota firewall. The old cab has more and thicker glass, thicker sheet metal and a shorter roof, all sitting farther forward then the same light stuff and the longer roof of the Dakota cab. At the same time, the Dakota front sheet metal sat forward of the front tires then the 49 sheet metal does, and the Dakota bed extended reward more then the 49 bed does. I used the Dakota bed floor on the 49,but the front of the bed was cut off the Dakota floor.

I don't have a clear side view of a Dakota cab less the front sheet metal, (I no longer have a good pic of the 49 cab less the front sheet metal), but a side by side comparison would make the difference very apparent.

UPDATE: The deed is done. It took longer to put the truck on 4 jack stands and round up the tools then it did to do the job. Unload the bars by backing out the adjusting bolts, tap the key off the end of the bar with a hammer, wiggle the bar out, and reverse the process for installation. After the bars are installed, determining how much to tighten the adjusting bolts is the biggest challenge. I set both bars with (about) the same amount of threads between the bolt head and the crossmember, then had to take the truck off the jack stands and bounce the front end. Farther adjustment required lifting the front tires off the ground and tightening (or loosening) which ever side is low (or too high). I did make one small adjustment on one bar (2 more turns of the bolt), but I suspect in about a week, more adjustments may be needed. I love having the ability to adjust the ride height by simply lifting the front tires off the ground and tightening or loosening a bolt (or both) a turn or two.

All 3 pictures were taken from under the truck with the camera upside down, so if they seem a bit strange, that may be the reason. It was much easier to get better pictures that way...

Pic 1) This is the key end of the bar. The end of the bar is flush with the end of the key. The farthest the bar can move back is 1/4" before it makes contact with the torsion bar crossmember. I suppose it could move forward, but with the tension on the bar at the adjusting bolt, I can't see that happening. It is something I will watch for at oil changes. Nothing has moved since the old bars were installed 3 years ago.

Pic 2) This is the control arm socket end of the t bar. The entire length (1") of the flats are inside of the socket.

Pic 3) This is the front end of the control arm socket. The tape shows 1 1/2" deep, and the full socket depth is 2 7/8". If the bar could slide backwards that 1/4", the full flats on the bar would still be inside of the socket, though it would be at the back end of the socket. At some point the end of that socket could wear, but that would be something I would address then, it would simply be replacing the lower control arm.

So what did I accomplish? I have 1 1/2" of threads between the key and the torsion bar crossmember with the bars set at ride height. Before the key was almost tight against the crossmember, and the ride height was about 2" lower then it is right now (that is about how much the truck has settled over the last 3 years). That is a pretty significant difference. I've taken the truck on a short run and do not notice much difference in the ride quality, and I suspect I won't be hearing any tire rubbing. Time will tell, but at this point I'm very happy.

pretty interesting indeed !
you, sir, are indeed the master of the dakota world !
glad it worked out just like you figured it would, and i for one will look forward to see how this works long term.
as the bars are thicker, i would think your adjustment[s] will hold, unless there is something else moving around. time will tell, but i think you may have this licked.
i was also pleased to hear the ride quality stayed virtually the same.

All so much to learn about these Dakota chasis going under a vintage pickup. At least my 2001 Dakota is the 4x2 model so it has conventional springs on the front suspension. But I wonder if there is ride height adjustment in the front end on the spring suspension Dakotas? Or just use shims under the springs if needed to adjust the ride height after I get the 56 mounted onto the Dakota chassis. In the rear I have a triangulated 4-bar system to install along with coil-over shocks. I may use an air-bag assist in the rear which would give me some ride height adjustment. The coil-overs will also allow some ride height adjustment with the preload collars. I'll have to make sure the coil-overs are fully booted as my 56 will be an all year/weather driver.

Andy, the front coil springs on a 2x4 Dakota are just like coil springs on anything else. Not much adjustment that can be done short of shimming them up or replacing them. The advantage with coil springs is there are probably many more options on different capacity replacement coil springs there there are replacement torsion bars.

According to everything I've read on the subject, the T bars in my truck were the highest capacity that fit my truck. The odds of finding a pair of 300-500 lbs higher capacity coil springs that would fit in the Dakota spring pocket are probably much higher.