2 more things. The wheelbase is a NON ISSUE. I can't believe that is being brought up on a chassis rated up to 11000#. Add in stability control, trailer sway control, ABS, EBD, big brakes, and all the other advantages of a modern truck like yours..... Wheelbase divided by the hitch to axle distance is far more telling than overall wheelbase anyhow. Shorter shank on the WDH helps this, I had a machine shop shorten and redrill mine.
Let that 5.0 rev. It is designed as a 7000rpm capable motor, and you will not hurt it in it's detuned state in the F150.