There is another recent post asking something similar. I believe 4.56 is the lowest you can go the 1500 diffs so that is what I would recommend....I would suggest lower if they offered but they don't. While doing the lower gears would be noticeable and make the truck feel better, don't expect to fully regain the power and fuel economy you had stock. While the gears can bring the RPM range back to close to stock it doesn't compensate for the big increase in weight and rolling resistance of the tires, or the increased aerodynamic drag of the lifted truck.
