[redmodelt]

I think it would be easier to flycut the recess above the pistons. Not much meat on the tops of the pistons to cut them shorter. Most people would be trying to increase compression and adjusting the spark rather then lowering it. Have you done compression check or clearance check with clay? Right now you are asking questions with too many unknowns? Like how much was taken off both? How thick the material is left on the head above the pistons? How far do the pistons pop up above the block? etc
I am thinking the 165 above is a typeo and might be 65LBS