[dave92cherokee]

Unless the engine in your xj is blown requiring the replacement then i'd leave the xj the way it is and use the cj to play with since everything's already installed and running. But if you have to replace the engine in your xj then you will need the entire engine and accessories, wiring harnesses, ECM (computer), probably the tranny and TCM (tranny computer) transfer case should be ok unless you just want to change it as well. I'm assuming that both vehicles have the same kind of tranny IE auto or manual otherwise that will make it harder. Easiest thing to do if possible is leave xj alone and play with the cj.