The saying was if you run 31" tire or larger use 4:56. If smaller go 4:10. I found 2100-2400 rpm at cruise was a good window for fuel and drivability. A short gear is fun to drive, but with high horsepower traction is a problem and you may find yourself looking for a taller gear. I use the words short and tall because we Americans often use High gear or low gear ratio to mean the opposite to their meaning. Example we will call a 3:55 gear a High gear ratio when it is actually numerically lower than a 4:56 gear which we refer to as a low gear. If you replace ratio with speed than it makes sense. Making a 3:55 a High speed gear and 4:56 a Low speed gear....