Cam, Compression ratio and octane ratings??? Help?!

OK, with those pistons, and an 1121G head gasket at .028" thick, I come up with the same 9.8:1 SCR as you did, with a DCR of 8.1, using a 73 cc head chamber volume. I would run it, make sure the cam was installed at the 'straight up' timing position (which will give you just the cams 4 degrees of ground-in advance), and start out with conservative ignition timing, like with the low teen's initial timing and work from there. Keep your ear tuned for pinging/knocking under hard acceleration especially when hot.

If you are concerned or run into an issue, you can very easily drop the CR with a thicker head gasket like the Felpro 1008 at .039" or the standard Flepro at around .051". For a DD and just tooling around, I would like the low end torque of a higher CR.