Pick up a 318 or continue my search for a 360

However, I have found a supposed working 318 with a 904 transmission and converter for $350. The owner knows little about it other that it was slightly modified and was running when pulled from the vehicle. He was only able to say that it came from a performance shop and was removed in favor of a crate engine. So in short the history of the engine is unknown.
Honestly, this is too easily just a 'story' to make motor that is totally unknown sound like a good running engine, with just enough excuses rolled in for the seller to feel blameless when it turns out to be a POC. ("I told you I was not totally sure, man....") I'd anticipate a rebuild with at least a 50/50 probability; i.e., flip a coin to determine the actual condition!