$15k would be reasonable in this market, and depending on thr real rust issues, it could be high. I believe that hood is also a 72-74. Makes me wonder if it were ever hit and replaced with parts from a 72.
I noticed that too, '71 was the only year with no D-O-D-G-E letters across the front of the hood.
If the car is close to stock, I would just get it running and enjoy it. 318 would make a good cruiser, would have the V8 rumble and decent on gas.
Might not need all that much to get it running. When I got my car (from a barn as well) it only needed a carb rebuild as far as the drivetrain went to get it going. Body looks presentable. I would just check for rust issues undeneath depending of the barn had a dirt floor or cement floor.