The motor alone is worth what you paid...and more if it is a 455 Buick motor. You stole the car but in order to do her up right, you're looking at dropping north of 15k. This assumes that you are outsourcing paint, metal and body work. The floor pans need to be cut out and replaced. I see a lot of metal and body work that needs to done as well. Not to say there is anything alarming, just a healthy pile of work. There are also the things you can't see - yet.
Find a nice garage and get this bird off the frame and build her right. I would also be sure to source a rear that can handle the torque that the motor puts down.
Good luck with this car. It's beautiful.