MitchF150 wrote:
To get that high tow rating on an F150, you have to have the HDPP and those are not on the used car lots. You might find a MaxTow equipped one and that's better, in that you get a bit more GVWR on the truck, but forget about towing an RV of that 'tow rating' size..
I have a 13 F150 MaxTow Eco with #7700 GVWR and I'm towing a #7000 loaded TT and that's about all I want to tow comfortably with it. It can tow more, has tons of power, but just for the shear comfort level of towing, it's all I want to tow with it.
You will run out of payload long before you reach any 'tow rating'.. So, choose wisely.. The newer Fords all have the auto engine start/stop feature.. No cylinder deactivation, and you can turn off the start/stop, but have to do that every time you start the truck..
To get the old 6.2l in an F150 you have to get the Raptor or a Platinum or higher trim level probably some 5+ years ago.. But, they don't have any payload left, so won't do you any good anyway..
Good luck! Mitch

The auto engine stop is deactivated whenever trailer lights are plugged in so it is a total non-issue when towing. And you can rig up some extra lights to use when not towing if you want a simple defeat mechanism but you really are better off just getting use to it.
The 3.5 turbo has a lot more torque than your 5.3 does and it won't lose torque in the mountains like a naturally aspirated engine does. I think that it address the issues expressed by the op. The 3/4 ton gasses would be a little more solid towing but would actually have less power, especially in the mountains, and would consume a lot more fuel when not towing. I regularly tow over 10,000lbs with my 2016 and think that you would be happy with one if you don't need the payload of a 3/4 ton. 2018 and newer models will have the 10 speed tranny which seems to be a nice improvement while towing.