Main bearing replacement benefits?

Can anyone tell me the benefits from installing new main bearings in my 89xj with 160k miles? I've got a leaking rear seal to replace. I might do the bearing job if it's worth it.

If you also add new rod bearings as well as new main bearings and replace the oil pump, there's a good chance you'll restore lost oil pressure and make the engine last a lot longer. It's all good and there's no downside to doing this (except the cost and time involved). Definitely worth it.

The main/rod bearings + an oil pump 1/4 of a poor mans rebuild, pulling the head and piston to hone the cylinders and replace the rings is another 1/4, having a valve job done the head and valves plus replacing valve stem seals is another 1/4 and then replacing all the remaining seals and timing chain and lifters is the final 1/4.

Its not a rebuild, and it doesn't bring all the tolerances back into spec, but it does get all the tolerances a lot closer to spec and helps the motor seal much better making it closer to being a 75k motor instead of a 250k motor.

Just throwing my two cents out there. But I went to Dodge truck school way back when (way before Jeep and Dodge became one). Jeep and Dodge used to share a lot of engineering philosphy and actually engineers. I was taught, if it is within *tolerance*, leave it alone. A good old part is better than an unknown new part and the old part has already succesfully worn in. The instructor told us, to get the new is better idea out of our heads. If the engineers think additional unit componants need to be changed, they will have a note in the manual. I grant you, tearing down a motor to replace one bearing sleeve is a little insane, way to much work for too little reward. But replacing good parts, with parts that may or may not be better and have to wear in some, can be an iffy thing.
New mains can be tricky, if they have worn ridges, the chance of metal to metal contact is greater. Remember in an ideal world, they are supposed to move on a film of oil. If they have worn more on one end than the other (or have ridges), the chances of getting a good match with a new bearing sleeve are slim, it may or may not wear in, before it self destructs. When metal to metal contact is made, it generates heat, the high and low spots, don't allow the heat to leach away as fast. Some of the heat is washed away in the oil, some is heat sunk into the crank and case. The results can be spalling, which accelerates the whole, wear until it disintegrates, process.
If I have a choice between too tight and too loose, I always choose loose. I measure and inspect before I change much of anything.