Probably not worth it anymore. Those cars are all monocoque-body, so the rust will likely have destroyed not only the sheetmetal but the structural elements too by now. It’s probably sitting for a reason.
“Probably not worth it anymore.”
These cars are getting VERY expensive. This makes restoring even total hopeless cases worth it. They even sell ENTIRE NEW REPRODUCTION BODIES for a Camaro or Mustang, with the doors hung, the whole shot. You can get virtually every part for a late 60’s Mustang or Camaro in reproduction, and some of the reproductions are from the original tooling. Chryslers are not as well supported, but this is improving.
You might have to put 30K into a basket case Camaro, but you might wind up with a car worth 50K and climbing...
Climbing...maybe. People who loved those cars are now in their peak earning years, and there are only so many cars to go around. Who will buy these cars when they are too old to drive or gone? I have seen a “peak” phenomenon in other “collectibles” - for example, Beatles cards. And, other than museum owners, who wants to own an “average person’s car” from the period between 1910-1930? They are hard to drive, can’t really go on all public roads, and take enormous amounts of (very unfamiliar) maintenance by today’s standards.