There are some threads out there on this. The XJ rear seat back is hinged on the sides of the backrest; the ZJ (w/ the 60/40 split seatback) has hinges that bolt to the floor board. The seat base likewise isn't a direct drop in and apparently also needs to be taken apart and some foam removed to allow the doors to close.
I didn't change the seats but did scavenge the rear seat headrests off a ZJ and installed them on mine. Threads out there on this as well.
As said above. You will be drilling holes for the new mounts.
I also drilled plastic on the rear seat (where your but goes) as you have to pop the fabric off, trim some foam and drill holes for the fabric to reattach to.
Its not to difficult.
Cool. Thanks. I knew about the bolt in fronts but didn't realize the G.Cherokee rear seat would fit as well. Once I get rid of my WJ and get back into an XJ, I'm definitely replacing the seats. Not that the XJ fronts are bad, but the ZJ/WJ are better. The rear seat on the other hand...that's a different story.