Kind of a chicken and the egg thing.
If you replace EVERY part of car A with parts from car B, C and D is the end result car A or car B or car C or car D?
I had a 56 Ford pickup, the cab was rusted I bought another cab. The frame was custom built, the engine was modern, the fenders were new the hood was from another truck, the rear end was from another car. Tires and wheels new. Etc.
So at what point is that truck the origional truck? And at what point is it not the origional truck?
If you replace one part at a time does that make it ok?
Why does the assembly of body panels welded together make it different than replacing a quarter panel, than a floor, then a rocker than....
Just tossing out thoughts.
Flame away