Howdy All:
Phil hit the nail on the head wigh code deciphering. Here's some more info. I gathered up all the head gaskets I had and measured for myself. Here's what I got.
Bore thickness
NOS OEM steel shim, D3DE 6051AA= 3.75" .028"
FoMoCo Composite, C9DE 6051 C = 3.81" .037"
Victor Composite, #3910 VC = 3.81" .046"
Fel Pro, #7916PT-1 = 3.81" .046"
Note that the "Thickness" referred to here is new, before torquing. For complete accuracy, measurements should be taken from an old torqued head gasket.
Those of you who have played with the Compression Calculator on our website please note that one of the variables is the bore of the head gasket. For greater accuracy be sure to insert the correct number for you situation.
Once again proof positive that the only way to know, for sure, what you have is to measure for yourself.
This is different than info previously posted by us and MarkP as to the thickness of the FelPro gasket. If anyone has a new or used Felpro, please mic and post the dimensions. As always we are still gathering information.
Adios, David