Here is another article that explains the calculation process as well.
www.carcraft.com/techarticles/calculate_compression_ratio
Assuming that the heads were not shaved during the machining process, they should be approx
64cc (vortec 906) correct?
Felpro 1003 head gasket
8.44cc calculated -
9.1cc advertised volume.
Pistons? Look at advertised specifications for vavle relief cc.
Block: is it O- decked or stock. Straght edge tool with dial indicator a TDC to determine this volume. Dial caliper would be sufficient unless you want the exact measurements.
You know that the block was bored out so the piston diameter for calculation purposes will be 4.020"
There is no quick answer here, however if you are persistanat and want to know the real deal. Do The Math.
My Gut feeling on this, as previously posted, is that if you put the Felpro 1003 head gaskets on this engine w/flat tops and vortec 906 heads, you will be fine on pump gas. I have run this combo 64cc heads w/flat tops and less than .002 deck height with no problems, however they were not vortec heads, but same combustion chamber volume.
Get a good calculator, pull out the old math skills from the past and get to work.
Good luck.