If the truck sees highway use it needs to be geared for that: 2200 or so at 65MPH for a SB and 1800-2000 at 65 for a BB or diesel would be pretty good. Offroad gearing should be handled with the transfer case and/or doubler.
Even for a trail only rig I wouldn't go below 4.56's because the gears start getting too fragile, especially with a D44 or 10b. Once again, it is better at that point to go with a crawl box/doubler, IMO.