Most sandwich-type head gaskets were in the neighborhood of .120" or so- - - -two thin pieces of steel sheet metal with a composition fiber layer between them. The heads had to be torqued, then the engine was run to operating temp, and the final torque sequence and readjustment of the valves was done after a cool down period. Supposedly, the sandwich-style gaskets would take a set and loosen the torque values on the initial run-in. In the 1960's Fel-Pro introduced a "no-retorque" sandwich gasket. There have always been single layer steel head gaskets of about .025" thickness that were intended to be installed with a thin layer of brush-on sealer which were used as OEM parts because they helped speed up the production line. I really doubt that engines coming off an assembly line got heat/retorque/adjust sequence. Any head gasket leaks probably got addressed in the dealer's service department under warranty.
Jerry
