If the motor recieved oil changes and air filter changes religiously, that motor is fine. Do a compression check both cold and hot and see what numbers you come up with. What does the oil look like now? what does the outside of the engine look like?
(dirty or somewhat clean like the PO attempted his best to keep it clean)
My Dad's 96ZJ with 230K+ on the motor still runs great, gets an average of 25 on the highway(bone stock, no mods, lift, larger tires etc). But he took VERY well care of the motor.
My YJ with about 120K+ turns out enough torque and power to break things. But like my Dad, I took care of my motor. And I just installed a turbo on mine and my motor loves it!:evil:
I hear that these motors are very strong if well taken care of. Can go upwards of 300K before a re-build. But I must stress the point, It all depends on HOW the motor was treated!
Some people will say that thier 4.0 died at less then 70K, but I would believe that the motor was abused(lack of oil changes, dirty filter)