I sold my 68 GTS 383 4 speed rolling body for $13.5 K.It was a 36,000 mile car with buildsheet,fender tag,and full history.The inner fenders were cut but I replaced them.The rear quarters were cut and I sold it with new AMD quarters,uninstalled.The car was 99.9% rustfree and the original interior was very nice.It still had 100% of it's original paint.It was missing the engine and exhaust manifolds everything else was there.It also was a driver before I pulled the engine.I had new brake lines,fuel tank,brakes,axles,rebuilt front end,and all 4 shocks were new.I had people try and tell me over and over it was only worth $6K,I knew better I sold it for $13.K.
I would say if the car is still a driver at least low teens and if it did not have primer over the original paint more...