I use 0.046” as the value for the Best Gasket head gasket thickness. Here are the gasket volumes for the various Best Gasket head gaskets when doing compression ratio calculations.
Best Gasket for regular bores 12.91” X 0.046” = 10.00cc
Best Gasket #572B (3.937” bore) 12.99” X 0.046” = 10.12cc
Best Gasket (4.030” bore) 13.35” X 0.046” = 10.69cc