Taken from the VP website..

C12
The best all around racing fuel made. Recommended for CRs below 15:1, satisfying the needs of 75% of today's race engines. One of the winningest fuels in racing history, including Modified Tour, GNN, D.I.R.T., Indy Lights, NHRA, AMA as well as other local and national championships across the U.S. and around the world.
Color: Green
Motor Octane 108
Specific Gravity: .717 at 60° F


Based on several dyno tests with different fuels (specifically engines similar to yours), I would say that C12 is what would work best. I would be very surprised if anything yielded any power gains. I am not saying that you couldn't experiment with something else, but beware of subtle detonation that will make short work of your motor. Those types of builds are very dtonation sensitive. Bob K has you running a ton of total advance IIRC-which could make it more octane sensitive.

MB