NO, not XJ, it's the ZJ's (mid-'94 -'98) that have the disc brakes.
You've got a 92, you may want to think about the proportioning valve from a 96+ XJ or possibly any ZJ, not sure... a search here or on the XJ forum will help you out a lot.
Anyways, it's the 1st-Gen Grand Cherokees (ZJ) that you want. All XJ's were drum rears unless some1 along the way did the upgrade to ZJ discs. Also, make sure that the ZJ donor axle is a D35 and not the D44-A. Another thing (which I'm fairly certain won't matter to you with the YJ) is that all ZJ's are ABS. Well, maybe one more thing - you may want to also do a search to see if the parking brake cable will be a problem attaching to the ZJ brakes...
ZJ's will fit what you're asking for. Cheap, direct fit (from a D35), and easy. And around here, about $49 including the ridiculous NYS "environmental fee" they impose on the u-pull.
"...a long habit of not thinking a thing wrong, gives it a superficial appearance of being right, and raises at first a formidable outcry in defense of custom. But tumult soon subsides. Time makes more converts than reason." Thomas Paine