Didn't think this was a hard question to ask just was after an estimate on value of such car restored to a thoroughbred level wasn't comparing it with any other car out there.
It's not a hard question, it's just that there aren't many samples to give an accurate number. Over 10 years ago I had heard that B. Perkins turned down $300k for his Thoroughbred level 1966 K fastback (non-GT). Does that mean the car is worth $300k?? Maybe, maybe not.
Even a concours trailer level car is not a clear cut case as there are factors in how well the restoration was done, how good of a car it was to start with, did it have a lot of sheet metal repair, were NOS parts or repro used?
Wish there was a better answer, but the best we can do is give a wide range, which really doesn't help much.