True, you can have ALL the HP or torque you want, more than you need, but if you are on a 35-40% grade, pulling a trailer, you may have the power, but the rear drive wheels will be spinning. Possibly even at gvw you could be spinning the rear wheels due to the wheels not having enough wt on them.
WHile I know many of you will laugh at this, but reality is, with a 400/800 motor in many of our pickups, while fun to drive, reality, my now sold 05 dmax dually had more than enough power for how I drive, even the gcw of upwards of 24-26K lbs, yeah I'm a bit over my "rated" 23K lbs. Heck, even the 2000 C2500 PULLING a 12K trailer with a gcwr of 13500 has plenty of umph. My 96 6.5td generally speaking had enough power, gearing for best speeds in between the shifts was a bit thin, but again, pulling my 12K equipment trailer with a gcwr from GM of 12500, no real issues. THis is the one that can go up a 30% grade at 20K lbs. My dmax was about 25% before literally stalling out due to too tall of gearing. Both with lower gearing, ability to get traction would have done more.
Marty