I get about 8.9 to 1 compression with your piston and bore dimensions, a Fel Pro 4.18 bore and .048 compressed thickness head gasket, and a guess of 72cc for 596 casting head.
If you do nothing but change to a Cometic head gasket with a 4.06 bore and .027 compressed thickness you are around 9.37 to 1 compression.
Then of course as the chamber gets smaller the numbers go up a little from there. Make sure you measure your chamber volume to get better numbers.