The Ford (and GM and Ram and Toyota) towing guides provide towing capacity numbers based on the engine and the gears for vehicles as that is all that matters. Gears can change the towing capacity by 25% or more for vehicles and most of the time people buy vehicles with gears that are too tall for the best towing performance.
The only time the weight of the truck comes into play is with the Combined Gross Weight Rating and for this everything is included including the vehicle's passengers and their pets.
The single best buy from any vehicle manufacturer is their tow package which will include a transmission cooler as part of the upgrades. It is all that is needed.