If the paint falls off the Mona Lisa and it is repainted by another artist using photos as reference, is it by Da Vinci?
I had thought the same until I saw what Janis Joplin's 356 Convert D sold for ($1.8 Million!) - it had all been repainted (and not by the original artist). There I guess it is more the providence of it being owned/driven by Janis than it being an old Porsche or sporting unique artwork.
The restoration of rusty Porsches has definitely spawned a lucrative craft of rebuilding them. Owners paying unGodly sums to restore and then not drive a "recreation".
In 1978 I bought a running (but no brakes) '62 356 Karmann Knotchback for $300. I fixed the driver's floor with the STOP sign at the end of the street. Those days are over! Marching build date steel wheels would probably go for $1000 - now! Kick myself for not storing it away in a dry barn.