Need some advice

First let me say I'm sorry if this posts twice. Im 29yo, been in the Army for the past 12 years and currently living in MO. I need some advice though because I'm thinking about buying a Duster. It's a 73 Duster, currently it has a rebuilt 318, auto, sublime, black interior, black exterior trim. Originally the car had a 340, 4-speed, gold with parliament viynl top. Needless to say I think the car is about 70% restored, the paint is recent, but sloppy, the exterior trim that was painted black is peeling off, all the weather stripping needs replaced and the current owner has no clue how many miles are on it because the speedo doesn't work. How much should I except to pay for this car?