I know I'm late to the party but;
Assuming the engine is already at plus .020 overbore, the swept comes to 658.96cc
Allowing 5cc for the mini eyebrows, 8.8 for the gasket, 64 for the heads, and 19.9 for the deck; this totals 97.7, Thus making your Scr 7.74, and
with the factory 248 cam in with an ICA of 52*, your
Static compression ratio of 7.74:1.
Effective stroke is 2.82 inches.
Your dynamic compression ratio is 6.73:1 .
Your dynamic cranking pressure is 127.42 PSI.
V/P (Volume to Pressure Index) is 105
Now that .040 cut on the heads might total 5cc tops (guessing), bringing your total volume down to 92.7, and the Scr to 8.11 max,so;
Static compression ratio of 8.11:1.
Effective stroke is 2.82 inches.
Your dynamic compression ratio is 7.05:1 .
Your dynamic cranking pressure is 135.50 PSI.
V/P (Volume to Pressure Index) is 111
So the compression boost is worth; 111/105=plus5.7% in low-rpm performance. Sweet!