XJ hitches do not fit MJs. The XJ hitch mounts to the underside of the "frame" rails. The MJ hitches mount to the sides. The best MJ hitch, IMHO, was made by a small company that no longer offers them for the MJ. Bradshaw's sells the brand, and they have confirmed that they can't get them for MJs.
Even the crappy Reese universal hitch for the XJ, which also fits my brother's Nissan pickup, isn't listed for the MJ. The MJ is perhaps the only vehicle in the whole world that hitch ISN'T listed for.