302 casting or 915 for 71 360 ???

If his 360 is a real 71 and still has the original 71 pistons, they will not be dished.

True on that, and if it were me, and the engine had a real only 20k miles on it, I wouldn't even remove the heads, id throw some new valve stem seals on it and put a mild cam in there and call it a day. No reason to put unported 318 heads on there. JMHO