I would say around $1000 to $1500 is the going price range depending on the condition. drive and look it over real good there could many hidden problems. Let it run at at idle for a long time or work it hard to make sure it doesn't run hot. If its Ok it should not get over 160 with the shutters open at idle and maybe 190 or 200 if under a hard load. look in the radiater to see if the water is circulating it should look like a river if Ok.
check for body work and how much is rusted out and dented or burned out around the exhaust..
Check the front end and steering for sloppy joints. they are not real tight when new but should not be so loose as to be hard to control the steering.