We have the same type of JK, 2 dr X 6 spd and it came with 3.21 gears, there should be a tag on the diff that says the ratio or the tooth count, you can divide those numbers and it will give you the ratio. With a JK you are limited to only a few ratios, they have unique gears to a JK, to my knowledge Superior only makes 4.88 and 5.13 and Alloy has 4.88 and 5.30 on the way. If that tire size is about a 35", I would go with the 4.88, that is what I have in my 2 dr with 35's. I had few problems with the ESP after the lift, even less after the gear swap. BTW, you will need a new carrier with the front gears, but not the rear.
Those of you that think you know everything really annoy those of us that do!