at one time (going back to 1999) Ford had a policy that if you already owned the trailer, they would lower the truck otherwise it was up to you to deal with. I have no idea if that is still the case. You can go over to:
Ford Powerstroke Diesel Forum
Diesel Forum - TheDieselStop.com
There are a lot of knowledgeable people over there. I do remember way back when the F250 had a 2" stop on the rear where the F350 had a 4" stop. Many were changing the rubber stops (they just screw on.).
Question. Have you attached the 5er to see how far the truck settles? And if it does if you have enough clearance when hooked up? That is what I found with my F350; after hooked up, it settled enough where I was ok.