definately get a donor vehicle. truck engines are easy enough to install, but you start to get limited on drive line length some times with a complete drive line from a truck
high output 4.0 jeep is a good driveline, xj cherokee donors can be found for under 5oo smackers to. don't forget no matter what you have wiring and computers that have to work in your yj
i wouldn't simply slap a carbed v8 in it, but thats just me.