I've searched for days and have not found a definitive answer; Will a 1997, 98, 99 xj SHORT block work in a 2000 xj. Heres the story. I got a 2000 xj for free but it had the cracked 0331. Bought a new improved head. Runs great but had the oil pressure issue (0) and a bad or collapsed lifter, ticking real bad at idle and certain rpms, got a little better when warmed up. 1st. repair replaced cracked head. 2nd. repair replaced oil pump and rod bearings, still have oil pressure issues and ticking, 3rd repair replaced rocker arms, bridges, and pivot blocks, still have issues, 4th repair changed lifters and cam bearings, oil pressure is now awesome but i still have the same lifter sounding noise. Now I'm pissed cause I had the head and pan off and could of checked pistons/ wrist pins for damage or wear and slammed one in but idiot me was sure it was the lifter/oil pressure/ cam bearing issue . I would like to put this head on a 97, 98, 99 short block since they are a little easier to find than an actual 00, 01 then rebuild mine or if I'm happy keep running the new combo. Thanks in advance, MECHANIC

 

Future reference, most oil pressure problems come from worn main bearings.
Unless your working on a 351 Cleveland/351M then its a lifter related, they had oil galleys to the lifters that was to large and lost oil pressure from there.

Back to your question, I haven't read anything to say it wouldn't interchange.
Just make sure you use all your original sending units and wire it up the same.
If it was mine though and you got all that into it, I;d tear it back down and slap
a set of rings and mains in it. Check the wrist pins while you have it apart then you know what you got.

 

I guess these 6's have issues with cam bearings, alot of people havings oil pressure issues especialy with 00 and up 4.0's in all the platforms. I finally found a couple of articles that convinced me to change out the cam bearings and that part worked out.

 

ya they have bearing issues after the oil is compromised with coolant from the "nice" cylinder head.

 

I've torn into plenty of engines with the milkshake especialy the late model chevys with the plastic gaskets but they dont seem to hurt the bearings as bad as I thought. I've heard that the jeep cam bearing issues were installed wrong or wrong clearances from the factory.