If you deal on a trashed-out piece of junk like that, invest in a big jar of Vaseline! It's already been picked over for all the good stuff. I wouldn't offer more than $250.00 for the whole rig, unless he's willing to let me hear the engine run, do a compression test, etc. He's already made his initial investment or close to it by selling bits & pieces, so whatever you're willing to give will be pure profit for the junk man. What do you intend to do with it once it's yours?
Jerry