you can put the stock motor back in or you can get a stroker that uses the same block & head. there are kits that will allow you to put chevy v8's in her. i would suggest sticking with the stock block just build her up.
check ebay & search "4.0 stroker". give you a rough idea

93 xj stroked 4.2 w/4.0 head avenger supercharged 6.5" long arm 35" buckshots rubicon 44's front & rear