F450 vs Ram 3500 DRW tow vehicle

If the 2020 Powerstroke has an identical shaped curve and if our trucks' computers will put us in the right gear for the load we have, to obtain the best fuel economy, 3.55 gears would allow it some good choices. With 3.55 gears in a F350 and a light load (150 hp which would be a large RV) and 65 mph we give the computer the choice of 2100 rpm and 37.5% load (430 NM is 37.5% load on that graph) or 1700 rpm and 533 NM or 1600 rpm and 566 NM. Hopefully the computer would choose 10th gear. With the f450 and 4.30 gears you don't give the computer a choice. It will run in 10 gear at 1900 rpm and about 42% load (477 NM).

Edit: It should be noted that the Cummins is tuned for a little higher rpm than the Powerstroke. (Powerstroke makes peak HP at 2600 rpm vs 2800 for the Cummins and peak torque at 1600 vs 17 or 1800 rpm for the Cummins). Likely the Powerstroke BSFC map would favor lower rpm.