Have you checked the DCR with both combinations? I would be concerned about the domed pistons with those head chamber sizes. The '63-'65 327 Corvettes used those type of pistons with 64cc heads, and the static compression ratio was 11.25:1. And I have a feeling that your cam does not have adequate overlap to bleed off enough compression to run pump gas. The DCR maximum for aluminum heads is 8.5 for 92 octane.