GM Head gasket Q

[Got Torque]

The old standard O.E. replacement steel shim gaskets are .018" compressed.
I forget exactly what the Mr. Gasket steel shim gaskets squish to, but right in that area.....

Now that you mention it i remember ripping a few newer 350's apart only to find the steel shim gasket on those as well the very old 350's i've been digging into.
I haven't gotten around to measure how far down the holes the slugs are yet, but i did take a closer look at the Etec heads. They seem to be very well optimized for a 4.030" bore to say the least!