I have the same truck except 2004.5 and a dually. I tow a 10k# fifth wheel and it does fine. The numbers I have limit the truck to about a 13,000# fifth wheel. The engine is capable enough but has a tendency to generate high exhaust gas temperatures on grades which is my limiter, not power. The transmission isn't perfect and I find my sweet spot for towing to be 62-65 mph in OD. Tow haul for any grade work. An exhaust brake is a must have. My original window sticker showed the axle ratio (3.73) if yours is still available. My truck weighs around 7,200# empty GCWR is 21,000#.
I am pleased with our truck and feel it makes a nice combo with our trailer. I have owned it for 5 years and it has always delivered us without drama or incident. I would have no problem hooking it up right now and head across country.
