302 heads

Also, if you read the MP engine manual....and I have said this ALOT, Larry Shepard clearly talks about when they "accidentally" found "swirl port" heads and it was LONG before the 308s were even thought about. He never cites a casting number, but from the context he was clearly talking about the early 70s. So that pretty much means all the heads through the 70s were actually swirl port heads. It's in the book. Read it.