Until you have the crank, rod, and piston in the block, you have no clue what the compression ratio will be. Deck height measurement is a huge factor.
Proper way is to put the piston a measured distance down in the cylinder, seal the rings with some grease, measure the volume, just like cc-ing a combustion chamber, and compare to a calculated volume.
Example: 4" bore, 1/2 down, calculate 103 cc. Actual measured cc, 115 cc's. Your dish would be 12 cc's. Then all you need is deck height, cyl head volume, head gasket thickness and volume.
