Someone finally made a suggestion on the 3 hour thread.....
Take off the distributor cap taking care to label the ingnition wires (you'll need to put them back in the exact same order they came off)
once the cap is off you should be looking at the ingintion rotor cap. this peice is held on with a single screw in the top center. again pay attention to the position this button is in. once this is off, you should be looking at the distributor base with the shaft coming up through the center. on the base there should be a black chunk of plastic in a "c" shape with wires coming out of each end. this device is called you ignition module. they are solid state devices that tend to wear out in older vehicles. what happens is when they get old, and get hot from the engine running, the components inside no longer make a good connection. this should be held in with two screws. replace this piece with a new one from your parts store and try it out.
Cherokeeforum is NOT as good as Wranglerforum, IMHO. There are a few good and knowledgable posters, but not near as many as on Wranglerforum. And they seem to be a lot less tolerant of newbies and such.