Incidentally, with a headwind, at least my gasser 6.2 won't hold 6th gear while carrying #3500 lbs.
It will drop down to 5th, and if you are going up a hill, it will drop down to 4th and if it's steeper, sometimes 3rd gear.
The Ford gas 6.2 has a horsepower and torque sweet spot around 3500-4k rpm. Yes it has low end grunt, but it will go to its sweet spot in tow/haul mode.
If you're coming from a diesel, and you don't like revving engines, you will probably not like it.
I happen to like revving gas engines. It's music to my ears.:)