Don't know your compression ratio, but am running a 327 with 650
edlebrock carb and simular guts as yours, but my flat top pistons
are only about 10.50 ratio and a small 268 comp cam....Personally
if I owned a vette, I would not worry about 91 or 93 octane gas.
Make sure timing not to hi. Heck i'm running 110 octane in a 57
chev, but it not a daily driver. I know others will chime in later on.