Jimmy,
I'd have to say that I respectfully disagree. These cars ARE jigsaw puzzles, and pieces were/are routinely interchanged...motors, bodywork, suspensions, trannys etc.
I know I'm not making things any simpler, but exactly what or how much constitutes an original is a huge gray area............. If I have the tub, but nothing else, do I have 1029? If I had to replace the tub, but have everything else, do I have 1029? If I have 49% of the tub, but everything else....you get the idea. Personally, I've always felt that the chassis was the essence of the car, but even these were reassigned in the day, so who's to say.
I know that a lot of people have made quite a good living in the "industry" of reconstituting cars (Sbarro etc), and many owners have a vested interest in a more liberal interpretation of what constitutes original....
Theoretically, it could get to the point where cars will be "built" around ever smaller fractions of original parts....to the point where parts will be hoarded so that multiple "original" cars can be built out of a single pile of bits and pieces..... Kinda reminds me of the "least publishable unit" theory of accademic papers....researchers present as little of their data/conclusions as possible in each individual paper, in order to extract the most possible number of papers out of any given project.
I have no solution, just to say "buyer beware".