It is hard to say. He says new suspension, but what does that mean? I would say bout $5-6k if the body is straight with no rust. The dash being modified like that is red flag for me. You just never know what gremlins you are going to find.
There was a 71 Dart posted here yesterday, but can't find the ad now. He was asking $1,700 and it looked super straight mostly stock with a slant 6. Figure take that car for $1,700 and put a nice motor and suspension setup/rear end etc and I'd bet you be in it for less than the cost of that one. Just keep looking, they are out there.