You will increase compression by about .2 for every .010 you remove from the deck height. You will also increase compression by for around every .025 you remove from the head. Every .025 off the head reduces chamber size by around 4-5 cc's. See the chart below. Here's a quick wallace racing comp calculation. You may have to mill the intake slightly if you take .025 or more off the heads.
350 bored .030 over. head gskt id 3.925 Piston belowdeck by .020 72 cc heads milled .025 to 67 cc. Compression = 9.59 Compression with 72 cc = 9.12
