I think restorers would normally claim to have at least some of the original airframe in the rebuild.
Peter Cazenove's Spitfire 1 which was landed wheels up on the beach at Calais in 1940 and recovered from the sands in 1980, is nearing the end of its rebuild to fly; the hulk looked reasonably complete at recovery and is presumably donating at least something to the finshed restoration. There are, I think, three other MK1s currently under rebuild with provenance...
However, there are several other Spitfire crash rebuilds around that seem to be from considerably more serious impact with terra firma and I do wonder just how much will be original.
Peter Arnold is the man to talk to; he does occasionally post on here, but you could probably contact him via the Flypast site - he is "PeterA" on there.