[Richard]

I typically shoot for about 2k at 70 in OD for a good compromise on performance and comfortable highway rpm. 4L80e with 4.10's will be just under 2k on 33's and going to 3.73's will lower rpm by about 150. Doubt there would be any gas milage difference between the two gears. 3.42's will lower rpm further. In my experience will hurt performance and gas mileage will not increase, may decrease. Calculations are at 70 with converter locked up, unlocked converter will jump rpms's about 200.