Maybe I just don't trust people, but I would have a hard time taking someone's word that the heads have been re-worked, haven't been run low on oil, haven't overheated, haven't been raced with NOS, the list goes on. I have seen too many people get taken advantage of when buying used engine parts. Unless the guy selling them is an engine shop and he is going to back them up with a warranty, I would steer clear. A thousand bucks is a lot of money.