Nope. Welding on the frame rails is fine, they are not high strength steel, and the factory welded on them plenty.
You don’t want to change out the rails on a rotisserie. How would you support the car on the rotisserie?
You want to put the chassis on a frame table (ideally), or at least set it up so that it’s level. Then you can check all the diagonals against the factory chassis specs. If you don’t have the factory chassis specs you can download the factory service manuals at mymopar.com.
Bracing the chassis before you remove and replace the rail is good, but you still have to measure everything before and after to do it right.
