sister is at a point to do something about her dakota with a bad frame , picked it up at auction last yr she figured it has 170k on so how bad could it be well she found out . after a month of driving she took it to the shop and they found frame issues .but every thing else is good
1st thought fix the frame
2nd get a frame from out west and switch every thing over (then can lower it and maybe switch the transmission she hates the lock up set up)

Having had a welding shop that repaired rusted frames, the hard reality is that frame may or may not be able to be fixed. It really depends on where the rust problem was located on the frame, and how bad it really was. If it was repairable and she drove it until it broke, its probably done for.

The word is, the Dakota frame was the same (provided you match cab to cab, and bed length to bed length) from the 1989-2003 (or when ever the truck changed at that time frame). Each cab and each bed length had a different wheel base. The 2 wheel drive frame is completely different then the 4x4 frame, not much interchanges between the two past the sheet metal and the drive trains themselves, but each drive has the mounts for the frame used.

Realistically, at 170K miles, she has a parts truck. Swapping the frame, unless you can do it all yourself, is not cost effective, and at those miles, the drive train is near the point of needing to be rebuilt. That sheet metal better be spotless and clean (looking at the front cab mounts and the driver side floor pan under your feet, are good starting points to determine if the sheet metal is worth moving to a different frame). I'm betting your sister is in a position of needing to buy a different vehicle.

I bought a 96 Dakota 4x4 with 44,000 miles on it for $400 because you could crumble the frame with your fingers. I moved the drive train to a different 4x4 frame, and put an old truck body on it. I've done several of these Dakota frame swaps under different vehicles. This 4x4 took 2200 hours, that is 11 months of 9-5 hours of actual labor time, at a fully equipped shop with an experienced worker, and around $8,000 in parts to get it road worthy. That was before I started on the body and paint work. Had I put another Dakota sheet metal on that frame, both the cost and the time frame may have been cut in 1/2, still pretty expensive and time consuming..

I too have had a few of those trucks. Like em better than the newer versions.
But I have to wonder how close that body is underneath to the next series, 97-04. Because I know where there is a frame from (I think it was) a 99 that's supposed to be clean.... I'll see it when I go get the other parts I'm getting from the guy in a week or so....

Most of the Dakota stuff I've dealt with were pre 97, but I've been informed (several times) that the 97-04 frames have the same cab/box mounting points, as long as the cads are the same, and the bed lengths are the same. Any on frame/ suspension replacement parts have to come from the year of the frame, and wiring and such follows the same model years of whatever you are using (and motor sizes & trans used).

I do know for a fact the 04 era frame change does not interchange with the earlier stuff. There is no part of the 04 and newer version of the Dakota frame that has straight sections.