You have the tricky transmission to offer gears for. 4.10 and 4.56 are the two good recommendations. You have a lower overdrive (.84, meaning 5-6% higher rpm than the .78 and .79 AX15 and NV3550).
4.10 would put you very close to where 4.56 is with the 5-speeds, and 4.56 would put that rpm a little higher on the highway. Personally I would go with 4.56 for the little bit of extra power.
I've found that even guys at "Jeep places" are pretty clueless, regardless of how long they've been installing gears or dealing with Jeeps or whatever it is they do at the Jeep place.
As far as overgearing is concerned, I would MUCH rather be overgeared than undergeared. The only thing overgearing will hurt is maybe the MPG a tiny bit if you love to drive way too fast. Otherwise it'll just give you more power at the expensive of some negligible rpm unless you're extremely overgeared.