Out here the Chevelles and Camaros are fetching close to 20k and still need total restoration. Big block 67-69 mustang fastbacks are nearly impossible to find, small block restorations selling in the 40k range. Right now a guy has a rotted out shell of a 1967 S code Fastback with no drive train, fenders, hood, deck lid, glass, interior or parts and wants 15.5k for it.
https://phoenix.craigslist.org/evl/cto/d/1967-mustang-fastback-code/6426204587.html
1957 Thunderbirds still fetch fair prices as do the 65-67 GTOs
In all, the older cars need to be factory special cars, SS, GT, Z28, R/T, etc to even hope to make a profit after restoration costs. If you keep an eye on craigslist every now and then a deal will pop up but they only last a couple of days. I missed out on a 66 GTO 4 speed that was pretty much complete with very nice looking chrome for $4k. It needed some lower quarters and 4 speed tunnel work but nothing out of the ordinary.