RPM vs. stock Manifold

Just out of curiosity, with 10.5 : 1 compression, what kind of fuel will you run?
The reason I ask is I'm planning a 340 rebuild and would like to do the same, but plan to lower it so I can run pump gas, unless I put out the bucks for aluminum heads, in which case, I'm told 10.5 might be OK.
Arlie