Jeep Strokers

Explain how i can achieve as much HP with out having to use higher grade fuels,
and explain why i would have to use higher grade fuels if i went to much bigger.

HP cost money, Gasoline makes so many HP ( BTUs ) per gallon. You can make a smaller displacment engine with higher compression, or a larger displacment engine with lower comprression. The high compression engine will require hi test, the low compression engine will not. If you put your foot into either one of them, you will still use a specific amount of gasoline per HP. One may be more efficient than the other, but because the engines would both be an AMC 6, you could get similer efficiencies out of either one.