My old Wagoneer had the same problem. It had a 360, though. If it's built anything like the 360s, the oil pump is intigrated into the timing chain cover, and a rebuild is costly. Not only do you have to buy the seals, but the guts, and if the housing itself is bad, the covers are very high. Mine turned into a nightmare & i finally sold it. The ticking, however was rather random, with the common being at startup, and it either going away after warm-up, or fading at any rpm above 1200. It ran like a top, but idling at 5 psi oil pressure kinda bothered me.
