Rear end gearing tech question

Dyno testing the engine does not just tell you what the maximum HP/Torque is at WOT. It is a graph of what those readings are at each rpm from starting to finishing RPM . What ever the max that the engine is capable of. That is very important in that you would generally want the cruising RPM's to be close to the best Torque/horsepower rpm to take advantage of that power. You can alter the rpms with trans gear ratios, manual trans gear ratios, tire diameter, Torque convertor stall speeds etc.. Or any combination of those variables.