Yeah, everyone with a 1/2 ton GM truck that has the 6 speed tranny should have gotten a 3.73 axle. To bad GM doesn't even offer it! As discussed many many times before, the 3.42 axle and 6 speed tranny is better than the old 4 speed and 4.10 axle.
With that said, if you truly stick to something that weighs <6000# loaded your rig should tow pretty good.
We towed a 5000# GWR hydbrid with a 2005 1/2 ton Suburban with a 3.42 axle and 4 speed with six of us and two dogs. That truck towed that trailer great. It also towed our current trailer fine but I was obviously short on payload with that set up.
You may find yourself towing in 4th gear most of the time (which is an underdrive gear), but might be surprised to be able to tow some in 5th. My Express will gladly tow our trailer in 5th gear, but my 3/4 ton Suburban with the 6L, 4 speed and 3.73 axle couldn't tow in 4th and had to use 3rd (direct or 1:1).