I didn't say a thing about putting 340/360 heads on anything. I said running a 4bbl carb on a mild 318 will not a problem. The slight mismatch between the 4bbl intake and the 318 heads won't be noticeable till you are so far into a 318 that you are foolish for not just building a 408 instead. A mild 318 will never notice it.

They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.