Keith Black pistons VS Speed Pro for 318

First thing I would do is measure your deck height with the new pistons installed. Then you can decide which way to go. If you are .010-.015 below, then leave it be and run the thinner gaskets. If you will have to cut the decks anyhow, then shoot for zero and run the thicker gasket. If you have already bought the gaskets, I suppose you can adjust the machine work accordingly, but this is going about it somewhat backwards. Also think about parts availability, you can get a normal .043 gasket from your neighborhood parts store.