Last time I checked, they never bring what you put into them. Knowing the guy who owns it, unless he has documentation on the engine I don't believe a word he says. I guess that's a risk you take buying used stuff.
In my opinion, it's about a 5-6K car as it sits. If he wanted to take the time to redo the interior, assemble the front of the car, and work out the bugs to make it drivable (down the highway, not just around his yard) then he might come close to his asking price.
http://www.ebay.com/itm/Plymouth-Du...111193255649&pt=US_Cars_Trucks#ht_15819wt_772
This car recently sold at an auction about an hour away from me for $5700. The only thing that I can visually tell has been done since it left that auction is they put carpet in it, the seats have new covers, and it has new exhaust. It's an original H-code 4-speed Duster someone put a big block in. This is what I would expect for a 10K A-body. Not necessarily an H-code car, but a nice presentable driver.