I have 38 inch tires and did the gear swap to 4:88s which I highly recommend. I am very pleased with the result. I think your MPG will improve as you are pushing a lot or tire and gear with that tranny in your current set up. I used a hypertech programmer to correct my speedo and got it right on, although I had to play with tire size as it only went up to 4:56. I recently went up against a non lifted factory tired 05 and pulled on him to 55 where he started to come back but seat of pants was a huge improvement. I dont downshift at all at 70 and only occasionally at 75. At eighty I am spinning 2500rpm exact. My mpg went from 11.7 before the lift,tires and gears to 10.2 after. The mpg goes to hell after 70 mph. I am obviously a fan of gear swap. The torque strain on the tranny and engine pushing those tires with a supercharger as got ot be immense. I think the heat and wear have got to be an issue. If your looking for pure fun, and not mechanical longevity, I dont think you can argue with a supercharger.
