Now more than ever, there is NO substitute for real paperwork, documentation, and OWNER HISTORY...
I agree - guys that want performance buy Edelbrock heads or the like, guys that want to build convincing fakes to defraud buyers LOVE repo heads, intakes,balancers, build sheets, P-O-P's, etc.
I have 2 '71 W30 cars, both with real window stickers, multiple build sheets, and bulletproof history (both purchased from their 2nd owners, one owned since '77, one since '71). 5 years ago I would have taken a chance on buying one without this kind of history, but not now.
Somebody mentioned 67 427/435 Vette guys and stampers- there is a reason why those cars aren't worth more, and it is coming our way
Colin