i run 2.73,,,with tremec trans,,,45 in 1st geat 80 in second 120 in third,,very nice,,il never use anything else,,,do the math before you choose a rear and u can choose when u want to shift,,,,so if u have 2.73 with lets say a 4th gear ratio of 1.00 u would be at 2150 rpm at 60mph with rouhgly a25 inch diameter tire,,,with 3.08 ud be at 2400 rpm in 4th ,3.27 would be at almost 2600 rppm in 4th,, and 3.55 will be at 2800 rpm in 4th, hope this helps