340 Pistons with 10.5 CR with X Heads???

when they advertise 9.5 cr you need to know the piston to deck height and head gasket thickness etc.. they used to calculate. Most I have seen are using a thick multi-layer head gasket at .040+, and they do make a gasket .020 thickness.

Keith Black makes a silvolite 1267 but they are 10.2 - closer