They didn't make high performance 318s except some kind of cop car Edition in the late seventies early '80s with 360 heads and 360 intake on it from the factory and they were smog motors...you want a 1968 318-3 steel crank truck engine
I'm on the lookout! Thought I found some special 318 today and glad I came here instead of handing over cash. Maybe I just need to go big block instead...