What octane should I run

At 11 to 1 or less = I run C11 but it is more expensive
for some crazy reason.

Higher compression than that I run C12.

The timeslips will tell you what your car prefers.

However, different fuel often takes a bit of experimentation
with Jetting and timing to optimize you combination.
But it is not a big difference.

But I won a class race in stockagainst another 340 at Denver Nationals
by .0001 true margin, bracket racing is not near as critical.