We have run 14.5 compression pistons 350X's on 104 with no problem, 110 and 114 gave no improvement. Actually the best gas you can use is the lowest octane that will allow operating without knock. More BTU's are released with lower octane fuels, faster..and they will "diesel" when used in higher compression piston applications causing the charge to explode as the piston is on the compression stroke, which is what your hear as "knock" or "ping".

MP red is 104 and works fine...used to be about $25.00/5 gal. pail, but may have gone up.