There is a thread running around the net about the 4.0 leaking at the head gasket where it is supposed to seal the pushrod side of the engine. One picture posted showed the same condition mine has, oil leaking down at the #2 cylinder area, onto the distributor, and back all the way to the exhaust crossing under the pan. I have changed the valve cover gasket, timing cover, front and rear main seal, and pan gasket, including a new sleeve on the harmonic balancer. It still leaks a quart a hundred miles, and I, too, am looking for a solution.
I presently think I might try the little whip cream can of Permatex "Foam a Gasket" at the junction, or JB weld, or just heli arc it with nickel rod . . .
Jeeps don't leak, they just mark their territory.