Looking through the latest Mopar rags, the amount of new metal & trim being reproduced is amazing. For E & B bods, its looking like cowls, roofs and practically every other piece is now available. If you suspend your dash and the pieces of non-rusted metal that just happen to contain the "numbers" from a string on the ceiling, and cut away and rebuild the car under them, using them as reference points, is that OK? Sure that's tongue-in-cheek, but it is not unconceivable that a resto can (and I'm sure has) require the replacement of 90% of the metal. These are referred to as "restorations", and accepted as "correct".
Now, what if, instead of piecing the car together underneath the hanging pieces (the "jig"), you instead assemble the same pieces used above on the other side of the garage, and when ready - slide the pre-assembled unit under the hanging pieces before finishing.. hmm - same result, different methodology.
Now lets say that you had a great "parts" car that had a lot of usable metal. Now of course you wouldn't need as much "repro" stuff, and could simply cutout the pieces that are good, and buy what's needed to finish up. Pre-assemble, slide under the "jig" hanging from the roof, and finish. Makes sense. Thats why I have parts cars lol. No different than above, even better because I was able to incorporate all those like-new and NOS parts I've been hoarding.
Now what if the parts car was so good, it only needed a little body work, and some small patches instead of full quarters. Sure, the trim needed replacing , and most of the interior was gutted. Oh well, Less work overall, same result. Slide in place and finish. Again. Same amount of metal replaced, same finished appearance, but... now is it a re-body
What is the difference?