okierver, we went from a 2002 F250 SRW 7.3L diesel to a 2014 F350 DRW 6.7L B20 diesel. Made a 100% improvement on pulling power, handling ride and downhill engine braking performance using speed control. When using the 2002, couldn't get any power at higher elevations (above 5K) to maintain constant speeds, plus the SRW handling was a touch on the iffy side as compared to having DRW. The 2002 torque was only around 550 while my 2014 is 800 at only 1600rpm. Couldn't come close the overall improvement for us pulling our 2013 3402RL which when fully outfitted for our road trips is around 15100+-. Hope this gives you some experience ideas.
Richard & Judy Blackwell
2014 F350 DRW 4x4 Diesel