There are a lot of us that are not over 14-16K gcwr with a 25 series truck. And for the most part, many of us only need the 3-4K payload of a 25 series truck. "I" do not need a 400/800 diesel. A 200-250HP and 450-550 torque motor with some of the newer 6 or 8 speed trannies, proper rear gearing for the tire diam and final drive ratio of the trans to go 60-62 mph at probably 1600-1800 rpm or so. Or 2200 like the MB van I drive for work......I'd be stylin! and a very happy camper. So I might slow to upper 40's or low 50's on the steeper freeway grades in the 5-8% range. No big, I expect that to happen, unlike some folks.
Marty