All crate motors come with build specs, and paper work including a cam spec sheet and usually a dyno report. I don't see why anybody who buys a crate motor would get rid of that documentation. So, might be a red flag.
Ask him which company he bought it from. Try to get a serial number from the block and call that company. They probably have a privacy policy, but just explain you are only trying to confirm whether or not it came from them. It's worth your time to do your due diligence, could save you from a disaster. Heck, if it's a recent motor, it may still be under warranty!
