If you have the 3 speed auto you should have 4.30 in the diff. Here is the info from the White Rabbit, my 2-door automatic build with the 3-speed:
Drive-train:
Engine: 1.6L 8v - 85hp, 89lb
Transmission - GM TH180/3L30 - 2.40, 1.47, 1:1
Transfer Case - Stock - 1.8:1, 1:1
Stock Axle and Tires:
Front Diff - Aluminum - 4.30:1
Rear Diff - Steel - 4.30:1
Tire - 205/75/15 - 27x8x15
Current Axle and Tires:
Front Diff - Steel + ARB - 5.12:1
Rear Diff - Steel + Mini-Spool - 5.12:1 - Swapped to 12 Bolt Rear End
Tire - 33x12.5x15 Pro-Comp Xterrain
The 4-door 8 valve manual Trackers have the 5.38, the 4-door automatic 3-speed should have the 4.625 gears.
With the 5.12 gears swapped in you should be perfect for the 30" tires, I would probably loose the 2" body lift as it won't be necessary with the 3" suspension lift. I find, like biker said, it's a bit of a dog on the road. It is fine up to 50 but she doesn't have a lot of top end, that is where his turbo probably helps the most. But with only 30" tires you might not run into that issue.
With a 4-door going with the Kicker 2 is a great option, and I might do it with my 4-door as well this winter. I found that running around on trails I needed the low range, but not 4 wheel drive, and I was just a bit over-geared for rock crawling. The extra t-case giving you a 5:1 would be perfect for playing on rocks while giving you the straight 1.8:1 for normal trail driving. Best of both worlds.
OOT industries is working on the Kicker 1 and Kicker 2 units again and hope to start making the Kicker 3 units again this winter. The Kicker2 unit is around 1200 or so.