Go knock on the guy's door and ask him if the truck is available. If it is, tell him what you know-" it's been sitting a long time,probably needs some major repair that you're willing to do, and you'll take it off his hands for a couple hundred bucks." If that doesn't work, at least it's a starting point. Find out how much he wants. If it's out of line, tell him thanks for his time and walk away. Look over your shoulder and say, "if you should change your mind, here's my phone number." Then go back to him and hand him a slip of paper you had already made up with your name and phone number on it. Say "see ya." and leave. Don't make another offer.
You've given him two chances to get rid of his old, broken down truck. If he wants to unload it he'll let you know right then. Good luck Scott.