I had a 2001. The limiting factor is the auto transmission and the 3:55 gears. Back then the manual transmission trucks were rated quite a bit higher. The srw can actually pull more than the duelly because the truck weighs less. Of course it can’t carry as much. Going to 4:10 gears will get you another 2000 lbs. That’s what I did because a lot of my towing is in the mountains. My 5th grossed out at just over 10K and I wouldn’t have wanted to go much higher. If you tow mostly on the flat, you should be OK with more. Invest in a transmission temperature gauge.