Headgasket for Kb399 and 302 Heads

Looking for some advice or a way to measure the clearance between the dome of the kb399 318 pistons to the cylinder head. The dome on these 318 pistons for those that don't know isn't on the quench pad it's in the valve area. Looking for high compression and with the pistons off they fit in the 302 heads. Would the .039 felpro gasket be enough?? Should I get clay and just set the head on the block to see how much room I have or has someone else on here ran this combo? Thanks

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