If you look on Robert Ash's web site, racingicons.com, there are a lot of original cars that still have a lot of their original pieces on them. It seems to me that the ones that were NOT raced in period have a better chance of having the original items on them and in them than the team cars, which were frequently rebuilt or modified. Ash's discussion of all this is illuminating and quite interesting.
Gelscoe's cars are said to be quite true to original and have gotten HTPs when the owner applied for them, so if you want to race and don't want to spend two million or more for a 60s GT40, they are the way to go. Or a Mark V. You're still talking about banging up an expensive item, but if one can afford it, why not.