Definitely need to spend a few hours going over all 4 in detail to see if 1.5 cars can be made out of all of it. Even if you can, are you better off getting a $6500 car that maybe needs less work?
But for a younger guy with space and time, $5000-5500 might not be a bad buy-in price to build a car and sell off lots of parts. That was me 25 years ago.