When these trucks were new on the lot, most of those with 5.3 v-8 had the 3.73 rear and came with the tow package. Like the others said, this consists of the trans cooler and hitch (frame receiver type - not bumper!). Most of the 4.8 v-8 were outfitted to be a less expensive alternative and didn't have the tow package. For only 2500 lbs, just add the trans cooler and hitch. And use the tow/haul mode selector. Do not tow in overdrive.
However, if you are towing a boat on & off a slimy boat ramp, the very best thing to have on a 2WD truck is the limited slip rear. I think these were made by Eaton and are real lim. slip units. I had a 4x4 and never had to use the 4x4 at the boat ramp because that limited slip would be enough. In fact, I pulled out a Toyota Tundra 2wd the first year they came out because it had no limited slip rear and the driver was stuck spinning his one rear wheel. I pulled him (Tundra + his boat) out easily with my Chevy.