I just measured the compressed thickness of the large outer gasket that came off an old 340 block with a plate. .075". Laying the filter plate block side down on a flat surface and measuring the distance from the center filter stud surface to the flat is about .110".

Checking the filter area on an old X block, the center attachment boss is approx. .080 higher than the outer gasket surface. Setting the plate on the bare block confirms the center boss is higher than the outer gasket surface.

This is just a few quick checks with some parts I have handy. Stacking any gaskets under center of the plate is asking for the outer gasket to leak based on what I see, Again, a smear of silicone is all I would chance using on the center of the plate.

Your parts may be different, but the fits can be checked with what you are using.


ETA... Just checked a second plate and it is substantially different - maybe .100" more offset center to outer surfaces. So, not all plates are the same. Ultimately the parts you have and how the block is machined will determine how you assemble yours. I would want a good crush on that outer gasket when done.