Hi all--
Oh boy...one of the more loaded questions again!

At this late date, one can fairly assume, I think, that a very good proportion of flyable WWII-era machines have become composites to at least some degree. As has been pointed out...that tended to begin while the aircraft were still in service. I've seen photos from wartime, for instance, showing a B-17G with the front half in bare metal and the back half OD/grey; the whole rear end had been cannibalized from a grounded (older) Fort. And the most singular such pic (seen before the days of digital imaging) showed a B-24 onto which had been grafted the entire nose from a B-17. (Heaven only knows why...! They did, after all, mass-produce both types!)
This issue is why, for instance, Sandy Thomson is operating a Sea Fury (and by all accounts absolutely loving it), with no paintjob at all save for a red spinner. Sandy told me he just isn't interested in putting the Fury in colours that imply originality when it is really a "parts" airplane. (Plus, it does look kind of cool and mysterious as it is...even if people do think it's an as-yet-unpainted P-47!) Many other owners would probably view this issue the other way up--make a "parts" warbird into the spitting image of a famous (and long-lost) original. Different strokes. In my own view...if it walks, quacks and flies like a duck, that, to me, pretty much makes it a duck! As has also been mentioned above, I just think it's tremendous that enthusiasts like myself can still see and hear these great machines firsthand, instead of only in old film clips. I remember seeing the TF-51 Mustang "Scat VII" at Geneseo a decade or so ago. Saw on the accompanying signage that she had formerly been the wild Lear-winged Reno racer "Vendetta". Nearly passed out from sheer delight. Realized, on reflection, that it was probable by this stage that little if any of the real "Scat VII" could possibly have been retained. And, standing there looking at an aircraft at least clearly linked to one of Robin Olds' P-51s...I did not care! It was simply a thrill to see it at all.
S.