Don't get me wrong, I can see this argument from both sides of the fence. I just thought the original question was about finding a more correct block for a real car, and its adding value, which I think it would a lot more in a real car than the same engine would in a clone/tribute, as they appeal to two entirely different types of buyers with entirely different intentions for their cars. This is a very complex debate, and sometimes leads to lengthy posts above. I personally wouldn't shell out the market value for some of these dated parts for a clone, since I don't think they're integral to the overall purpose of a clone/tribute car's being built. For a real car, sure, the rare parts are worth the big $$$ to have a "more complete" real car in the end, which is what we're all after right?
Jeff makes a valid point too, no one is owed these rare parts because they happen to have a real car. Market value is determined by all the people that want them, for whatever the intended purpose. There are lots of people who have real supercar parts but no real supercars, myself included, and I don't see anyone lining up to give us a deal on a real car. I guess that's the rub of the free market society, but that's the good ol' US of A.