4.0L Swap

Just got me a sweet deal on a '97 4x4 XJ loaded! Only problem is that the guy I bought it off of has no idea about cars "under the hood". He had a cooling problem and took it to his local shade tree. when I got the Jeep a week ago the cracked head, cover, intake, and exhaust was off and in the back hatch. I know that Jeep changed the 4.0L some during its hay-day, but I need help knowing what vintage motor is needed. I have been asking around town here for a couple of days now and have been getting a lot of different answers. All I want to do is replace the long block, and/or whole motor, which ever I can get away with cheaper, everyone's on a budget ya know. Can anyone help? Do I need to look for casting numbers on the block, head... etc. Or do I just need to look for '97 donor? I have a running '93 4.0L, but from what I've been told thus far it won't "really" work. Sorry I'm rambling.... Help!!  

It is possible that it only needs a new head. Six's have a nasty habit of cracking heads when they overheat so you might want to check cooling system or replace radiator regardless of what you do.