i need a little 340 help. Lets Talk head gaskets

Measure your stroke (stock should be 3.31) and how far above the deck the flat on the piston is above deck at tdc with a bridge depth mic. If you need to check clearance front to rear with clay, you can also use a pair of FelPro 518SD gaskets on one side to come up with a .120-.125 inch spacer.