Is the truck in question the Yukon in your pic? What year/motor?
I run a 350 vortec with 3.42s in a 1500 and have hauled some heavy loads (some over 2000lbs) in the bed and haven't had any problems, plenty of power in just about every situation. Can't speak for towing though, haven't done much (just some short runs).
The nice part about the 3.42s is they are relatively good on gas on the 4-lane. Personally, I wouldn't want anything lower, truck does everything I need it to (daily driver/farm truck)
Just sharing my experience with that gear ratio/motor/truck setup, I can't speak for others.