My first XJ was a 92 with a 4.0. I got it cheap B/C previous owner ran it low on oil and collapsed a lifter. It was tapping badly and parents of owner were afraid it would strand Tommy Teenager. Jeep had 270,000 on the clock so they did not wish to put any more money into it. I tried everything to get the lifter to recover, it would not. We drove it like that for another three years, other than embarassing noise it ran great.
Everything Winterbeater says is accurate. You can get adjustable pushrods but if your lifters are worn out that would probably cause damage to the camshaft. You didn't change to a higher viscosity oil recently did you?