It seems that the OP is talking about two different units in his question. He is seeking info on an upgrade to a DP vs his currnet HR unit.
In my experience with the prospective upgrade to a 325 hp DP unit the drivetrain of engine, trans and rearend are more than capable of towing of a F-150 truck and HD cycle in the bed. The limiting factor is the hitch.
After inspecting the rear frame and hitch If I was satisfied that the frame was adequate I would upgrade the hitch to a 10k rated one and add supplemental braking to the truck and go about my business.
I can't say that I have personally worried about this point and have towed my 2009 Silverado for over 30k miles quite successfully behind my 2003 Newmar Dutch Star. I do inspect the hitch and its attachment points including fasteners at least annually and have seen no signs of any looming problems. Towing a trailer places a significant tongue load on a hitch where towing a four down toad is completely opposite, with its loads being fore and aft with minimal vertical stresses.