Do you have an automatic or manual transmission? You'll want 4.88's if you have a manual and 5.13 if you have the automatic. You need a 3" lift.
I have an automatic 4 door 2007 Sahara, which came with 4.10 gears from the factory.
bone stock with stock 18" wheels and 32" street tires (standard sahara setup) 19 mpg
switched to 17 X 9 wheels and 315/70-17 BFG AT kept stock gearing 12 mpg
regeared the differentials to 5.13 and was surprised at 17 mpg
I have a long list of things I usually include when I answer this question, but I don't feel like doing that right now. If I remember right, I turn 2,400 rpm's at 70 mph. It's been a few weeks since I have been home.
2014 Copperhead Pearl Unlimited Sahara in progress