Exactly ^^^^^^

clicked on this thought I was in the porn section LOL

Hope you where expecting more than an exploding head. hah !

Pace performance 5100 502 short block. What 454 you now have? what gen? Gen 6 mag cam is same as 415 502 mag. No 502 were built with cast pistons or cranks, at least not by GM. the only long blocks merc built were blue.

No difference between the GM ZZ502 and the Merc 502 shortblock other than the oil relief valve, oil pan, the cam, flywheel (GM comes with flexplate) and a heavy coat of black paint. Use the cam you have in the 454 Mag if its a roller, or find one (454 Mag or 502 Mag are the same), and change out the oil relief. I just purchased a ZZ502 shortblock and the freeze plugs are no longer brass, NO Worries< they are now stainless. I believe GM performance offers this engine with iron rectangle heads. May want to ensure it has marine type head gaskets if you purchase with heads.