My 2014 F450 Platinum with H&S and 4:30s was amazing to tow with. Howver, on the highway it was awful. way too much gear. I had 22.5 then 24" wheels both with tires that were just about 37" tall and that helped out big time. I could cruise at 75mph and I believe the rpm was around 2200
I think that rpm would be perfect. I'm going to run mine in 5th the next time I'm pulling heavy and see what 2200rpms nets me for mpg. I think 2000 in 5th calculates to 63mph with 34.3" tall tires and 3.73's.