Hi jhdwrench,

Unfortunately, I don't which year you're asking about.  You could try the following links to figure out what size and offset wheels/tires you can run.  Your lift kit question would best be asked by a 4x4 specialist/outlet.

http://www.tirerack.com/
http://www.discounttiredirect.com/

Good luck!

If it is a 1997 or newer you will be fine with 31" and stock wheels

31x10.50's will work fine. 12.50's will need offset. I dont see why you would want 31x12.50s though. It will look like a lawnmower. haha. 10.50s are what are on mine and they look plenty wide.

i fit 32s

I'd recommend 31x10.5. You may experience light rubbing in the wheel well at full suspension compression but most of the time it should be fine. Also, you may experience light rubbing at full steering lock which can be solved by installing washers.

You need a lift kit. A shakle lift will suffice but you need something. Without a lift the tires will fill the entire wheel well and you will have NO flex. Mine were 31x10.5 they were just a touch too narrow for my tastes but I didn't want to spend the money for new wheels with the proper offset for 12.5 wides. You can also run spacers if you want to to make room for 12.5s