CJ
Carl is the machinist in the group, and could probably figure this put in a minute or two, but I think it would be difficult to determine the right end play in a completed assembly.� I bought a NOS gasket for my replacement, after the lock up, and I noticed a couple of things.� First it was thicker, and John at Midwest can tell,us the correct dimension, but I also noticed that the material was different between the two gaskets.� The NOS gasket was thicker, stiffer and did not seem to be affected by the oil, while the Felpro was thinner, less resilient and seemed to absorb the oil and become almost mushy.
That said, was I to try to measure them I would try to compress a portion of one between two flat metal rulers, like the 6 inch one in Carl's shirt pocket

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That would compress a large portion of the gasket without deforming it, use a micrometer and you can measure the thickness of the rulers and just subtract to get the material thickness.
Gun