I have the same rig you have. I changed out the rear end to a 3.73, installed a rear sway bar, flipchip, max tranny cooler with a tranny temp gauge, and a class IV hitch. I pull a little over 5000lbs with no trouble. I thought about upgrading the radiator to the larger one but the engine never gets over 210 degrees towing over the passes in the summer so I think it's alright. Total cost of these mods was about $900-$1000. Since its my daily ride I like the 4.6l with the flipchip, quite peppy and economical.