Why do you want a 4 banger when you could have a nice 6 banger that lives forever??? Here is my earlier post of a guy I met with lots of xj/mj's sitting around:
I meet a guy in Willits who has 5 xj's & 1 mj behind his "Rock Store." He has a huge Suburban on 36/14.50x16.5 Mickey Thompson Baja's in front of his shop as of yesterday. He got all those rigs for $400 as people just seem to give there old xj/mj's to him. He's a sort of magnet in the area I guess. I know his parts would work for you and be cheap. Give him a call if you are interested. I think his name was "Dave" (707)459-1206. His address is 1793 S. Main Street Willits, CA 95490. He should sell you the stuff you need dirt cheap, he got them for free anyways. He had like 3 87+ 4.0L & 2 pre 87' I think & 1 mj that was 2 wheel drive. He had 2 4.0L Renix motors pulled that I saw. His son is the gear head so you might want to talk to him.
Troy