If you change tire size, you *need* something like the AEV procal. Super-important for accurate speed, ESP recovery calculations, and also shift point adjustment for the automatic, if you're interested in doing your tire swap properly.

Gear ratios...You've probably got the 3.21. You might have the 3.73 if you Jeep came from the factory with a towing package. Do a search on here--you can tell for sure by counting the number of turns the driveshaft makes as compared to the number of turns one of the rear wheels make. There's a writeup on the procedure somewhere around here.

You can also go to the Jeep website and take a look at what the original window sticker listed your gear ratio as. You'll need to type in your VIN at the end of this address after the "="

http://www.chrysler.com/hostd/window...kerPdf.do?vin=

Regardless of what axle ratio you have, your Jeep is going to go down the road. It might feel a bit sluggish with the 3.21 especially on the highway. If you plan to do any crawling or trails with a lot of elevation gain, I'd opt for a higher axle ratio, 4.10 or more.

Regarding the steering stabilizer, your Jeep has one from the factory. It's basically a shock absorber mounted with the steering rack. I'd upgrade that only if you do some wheeling and determine you're getting too much bump-steer (steering wheel violently thrown around by obstacles you encounter). I've used the stock one and it's fine for my purposes.