Super low compression is a dinosaur thing. Those Panchitos not only flow better, but will mix the fuel and air better. You'll have so much speed on the intake that the swirl will be better too. I'd up the compression to 9:1 minimum. FYI, I run 9.8:1 on 93 Octane Ultra(with 10% ethanol) in Headflow Masters 44 x 37 heads in a Raby 2165cc.
Gene Berg has been gone a while, and the low compression motors of old should go away these days. Alcohol in the fuel actually deters knock/detonation. All you have to do is pull back the timing a couple degrees at a time until the knock goes away. Try 32, then 30, then 28. I seriously doubt a high compression 1776 with Panchitos is going to knock. But talk to Pat Downs, he knows what to do.
Oh, and REALLY good choice on the heads, they are exactly what they are cracked-up to be.