I've hauled a BobCat in mine numerous times, which weighs more than 2000 lbs. I've towed a travel trailer that weighs 10,000 lbs+ a few times through the mountains. Neither seemed to matter much to the truck, I was impressed.
I have a 1998 half ton supercab XLT 5.4 with the 4x4OffRoad pkg and heavy duty axle.
Well, I sure wouldn't do it on a regular basis, but the truck did it just fine. The trailer was 33 feet, a luxury model and heavy. I once towed a 24 foot trailer with a 4Runner, it pulled it just fine but in an emergency there would have been hell to pay I bet... At any rate, the 5.4 is impressive that way. It doesn't really feel all that powerful (and really you can blame that on the transmission - if you want to feel how a transmission *should* feel drive a Toyota Tundra, or any V8 Chevy...) but as you load it up it seems to make the needed power and just goes. Really has impressed me a few times.