What's my big block 75 Duster worth?

As far as the body goes, hood, roof, and decklid are straight. The fenders both look good, the doors have no rust but a few waves and dents. The quarter panels have the same story, a wave or dent here and there. The worst offender is the rear driver quarter. It has been patched and they didn't do a great job. Floors and trunk look good. It's a Texas car so the underside looks fine.