[MagicRat]

If you get a doner frame, don't swap it all at once. There is a better way.

Swapping a frame all at once is a huge logistical nightmare. You need hoists, lots of BIG jackstands, lots of space, and lot and lots of time. You would have to remove the entire front clip, driveline, suspension, axles, bumpers, body, wiring, fuel system, brake lines etc.

However, I recall the frame rust on your car starts approx. under the drivers seat and goes back, right? It is MUCH easier to have a good welder cut-out the rear two thirds of the existing frame, then cut out the same pieces from the donor frame and weld it (using overlapping plates) to the existing front third of your frame.
This means the front clip, driveline, wiring etc can all stay in place, and would only take a fraction of the work.

I did this on my '68 Thunderbird a few years ago....... it's MUCH easier than pulling off the entire body etc etc.