the first place i started was to find a 4.2 crank. You can buy a new one if you want but i thought it was more cost effective to get a unturned used one. Just look on craigslist too because there are always people selling off a older 4.2. you may want to just buy the whole engine becasue you will need the rods too. Jeepstrokers is a very informative site and everyone there is willing to help even if you've never built an engine before. If you have any questions dont hesitate to ask.
89' white XJ,4.0L, Auto, 2/2.5 RE lift, stock axles, 31" sport kings on wagon wheels, lights on roof rack and bumper-Sold
2000 XJ, 4.0 L, AW4, Dana 30/Chrysler 8.25, 3" skyjacker lift kit with 31" MTZ's, Hella 500FF, upgraded headlight harness and some extras.