Jason, IMHO- If your really set on locking the rear get in touch with ARB and go with an air locker. However, be ready to pay as it won't be cheap. http://www.arbusa.com/uploads/PDF/ac...CherokeeWK.pdf
Keep in mind that either way you'll have to have your gears setup again since your changing carriers. Something not typically for the average DIY. Most local shops around me charge about 500-600. Once you start to add things up it's going to get pretty expensive.
Maybe check your local salvage yards for a complete ELSD axle and try to figure out how to make the wiring work?
Good Luck Man!