No more than 12k. Quarters need a lot of work. Door is junk. My guess is it will likely need floor patches from being outside. Motor, while rebuilt, is out of the car. It will be a labor of love. It's worth it, but figure 15k to straighten the body correctly, with new paint and new top. another 2k for engine related pieces. Radiator, manifolds, new exhaust, carb. You'll be in it for $30k.
Hopefully you could see it for that. I bought a 68 400 4 speed convertible project from this site. All in, I may be sitting at close to $30k for the full restoration which includes the price of the car. I'm about 60% completion on it now.
If you like the car and can get it under 12k, you won't lose your [censored]. LOL