I've calculated in the ballpark of 11.3 to 1.
I have Factory 596 heads that rate anywheres from 68 to 72 cc's... According to my research at any rate on those and I've just guessed 70cc's.. that's an icon flat top with valve reliefs, .010 above deck with a 4.040 bore... And a felpro 1008 .039 gaskets...