A re-body is a car whose VIN plate, fender tag, and title are from a "donor" car, and the body with the numbers stamped in the radiator shroud and cowl do not match the VIN. IE...A totalled or rusted out 383 71 Challenger R/T was stripped of it's VIN plate, fender tag and maybe drivers door, then those pieces were put on a clean 318 71 Challenger and the 318 car was built to look like a 383 R/T. If you REALLY get into it, and you can save the radiator support and cowl from the R/T, you could graft those pieces onto the 318 car. The car would be titled as a 383 R/T.
As far as value of a 383 auto 71 R/T in true #1 national show condition...I'd venture at least 50-60K. It better be PERFECT, and be fully documented, and NO questions about it's heritage at all. To the right buyer, even more $$$ is possible.
Funny combination of questions has me
Can you elaborate?