First, you have to figure out what T-case you have. I am assuming that you have a four cylinder since you did not say. If my memory serves me right, there were two cases in the four cylinder in that year but I could be wrong. You need the gear drive case and you can put different gear sets in it. There are 4.0, 4.70, and 5.0. The inside of the t-case has to be milled a bit but it is not that hard to do. The only problem with doing the gear sets is it does not retain the stock low gear in the t-case; you have the normal four WD high range and a very low, low range.

You should really read up on this stuff on one of the web pages I posted. Marlin is the pioneer behind the low gears and the dual case setups. His stuff is all I will use and have been for the last thirteen years without a problem.