I checked my engine speeds against actual ground speed on a recent trip, photos are attached.
With my stock 2004 D2 gears and 285/75/16 tires, the following applies (give or take a few percent error):
60 mph = 2,000 rpm
70 mph = 2,300 rpm
80 mph = 2,700 rpm
90 mph = 3,000 rpm
This was fully loaded with camping gear, tools, wood, steel bumpers front & rear, winch, steel sliders, skid plates, etc. My truck feels plenty peppy around town and it climbs hills fine. On very steep, long inclines it may bog down in 3rd gear to about 65 mph but nothing as bad as my old '96 D1. It's certainly not a sports car but it is what it is. I've never longed for shorter gears. Note that my speedometer reads about 10% low.