That was the problem with her 2500. It had 3.42 gears, so you had to do 80 or better to keep it in 6th gear.
But she doesn't want to go nearly as fast with her horse trailer.
And 80 happens to be my preferred speed with my 3500, but that's also at 2,000 rpm. Which it really likes, by the way. Realistically, I should have 4.10s for the weights I pull at times, but then I probably would end up going slower.