Yes, I have done this upgrade!
Your axle is the same as the 1991-2000 explorers. Except that the brakes were Drum from 91 till 94. So if you want to upgrade to LS, then all you would have to do, is get a LS carrier complete with spider gears, (any gear ration, thou you do not need the ring gear, since you will be re-using yours.) I would suggest that you get new Bearings, and maybe new clutches, both depending on how many miles on the LS carrier. You would have to re-use your Ring gear since it is already matched to your Pinion gear. Now let me tell you this, It could be a difficult process to get the correct ammount of backlash set, I believe you have to change shims, and stuff like that. If I were you, I'd have someone who know what they are doing, do the job for you. But my point here is that you do NOT have to change your Axle to obtain LS, just change your Carrier. Sometimes you can find LS carriers here in the For Sale Forum, or E-Bay, sometimes even the Jeep guys sell them when they put the 8.8 in their Jeeps. I hope I have helped out, if you have any questions, feel free to e-mail me......