If you have some fab skills you can buy the RC drop brackets for an XJ. The brackets will fit but the braces won't, some people remove the MJs added reinforcement which allows them to fit like they would on an XJ.
Personally I don't like thier braces so I would use the brackets and make new braces that extend to the cross member. The RC brackets are cheaper and you don't have to deal with RRO.
Or you could always do like I did and just make a set of brackets, its time consuming but not terribly difficult if you have some fab skills.