How much is it?

Hi, I know a guy who has a 1974 Stingray with a 454. the guy has like no interest in it what so ever. it's been sitting in my garage for almost a year and the guy hasn't said a word about it. i think he might just want to get rid of it. i was planning on making him an offer on it but i dont know how much i should offer him.
  the car has seen a lot better days. it needs a new paint job. is missing some of the minor interior parts and emblems. it was origanly an automatic but my dad and i converted it over to a 5-speed. the engine could use a minor tune up. and i know he didnt pay a lot for it to begin with. it does have some nice custom side pipes and good tires.