Cylinder head discussion 340 with stock above deck pistons

I see @Inertia has not answered yet. The stock amount for the early 340 positive deck height I believe is "around" .025" if I remember correctly. What I would do is allow the head gasket to set your quench distance. That's the easiest way to do it. Just let compression "fall where it may". It's gonna be pretty good, regardless.

Regarding the aluminum head changing compression theory. Look at it like this. Compression ratio is a physical comparison. It is a comparison of the cylinder volume at TDC to the cylinder volume at BDC. Let's say the volume of your cylinder is 1/12 the size at TDC than it is at BDC. Then you have a 12:1 compression ratio. Understand? That ratio, or comparison hasn't a thing to do with "whatever" material the cylinder head is made of. The head could be carved out of hickory and the compression ratio does not change, since it is a physical measurement and a physical comparison of volume. That volume doesn't care what material is around it. It's just volume.