8 1/4 vs. 8 3/4

Looking at one of those rpm calculators - 4th gear = 1:1 (355's) with 26in. Tire, 115pmh @ about 5200rpm's. Now I'm totally guessing 5200rpm's is going to be this motors sweet spot ???? IF and thats a big ( IF ) I can pull off 115mph - I'm hoping to pull off a low 12 and dare i dream ? High 11's ! !??