[comptiger5000]

The 5.9 doesn't have cooling issues, per se, but it doesn't have a lot of extra cooling capacity. Keep in mind, it has an e-fan, rather than the mech fan. The ZJ was already a warm running vehicle under heavy load (such as towing), so the bigger engine was enough to push it a bit farther. The hood vents don't flow a heck of a lot anyway.

As far as your running temp, it sounds like it's running way too cold (2nd mark left of 210* is 155*). I'd say it's time for a new 195* t-stat. It should run between the mark left of 210* and the 210* mark itself pretty much all the time.

I'd move your grill block to keep the tranny cooler unblocked personally. These trannies don't like heat at all. Mine actually didn't have the factory tranny cooler (not included on 98s), so I added one.