buying an a body

hi guys getting back into the mopar world again i used to owner a 1990 dodge ramcharger that was rust free very nice truck and i loved it but i sold it and bought a camaro because i wanted a muscle car. now i want to get a mopar a good friend of mine has a couple of old mopars he has one that he wants to sell me and its a 1972 dodge demon. the car is pretty rust free but the car was hit on the rear quater panel right behind the door the trunk is rusty to and the drivers door has a couple of dents in it. it has disc brakes in the front with an 8 3/4 rear end no idea on gear ratio and it has a slant 6 in it the car is pretty much all there but i have no idea what it is worth if you guys could help me out that would be great and it is an auto with no a/c