A clean car with a restoration done to what was needed and done right, it's a deal at $10,500 IMO. The guy has that much in it at least, the labor alone would be more than that at a shop. I'd still knock him down to 9k.
Wagons are hot...add $2,000 to the asking price. http://www.stationwagonforums.com/forums/threads/1975-olds-vista-cruiser.37521/