you can, just need the master and booster from a non abs, then maybe some brake lines, and you'll need a proportioning valve in line, and then take the bulb out of the dash like most guys do.
Not sure what year you have, but I have a 91 that had ABS. I now have a 95 XJ vacuum booster and m/c. I also grabbed the pedal assembly fron the same XJ. Works so much better. The hardest part for me was plumming the stock lines into the porportioning valve just because the bends and port are off from the ABS version. I ended up just getting a new line for the left front.
yah you'll want to be comfortable bending/flaring brakelines when you do this sorta thing. ive had to replace all the hard lines on 3-4 rigs in the last year or 3 and its a pain every time, but i just hate double flaring brake line.