So @pishta was wondering about the OEM slant 6 steel shim head gasket thicknesses. I have the answers. I recently acquired an NOS steel shim gasket from @volaredon, thank you , Don. I already had an old one I saved. So here is what I found out. First, I measured the old one in an area that was not embossed, but just flat. As you see, I got .015". Next, I measured the embossed fire ring on the old gasket. As you can see here, I got about .019". Next, I measured the new head gasket in the same unembossed spot I did the old one. As you can see, I got the same .015" that the old gasket measured. Finally, I measured the uncompressed fire ring on the new gasket. You can see I came up with about .040". Both the old and new gaskets measured the same gasket bore diameter of 3.560".