I have the Palfinger Badger on my 5500 to haul my truck camper, but it has a gooseneck inset for future use. I chose the Palfinger because it had a low skirt in the rear allowing me to mount a SuperHitch Magnum receiver off the rear.
I assume you will be getting the 84" CA model 4500 that has longer wheelbase. This should give you the room to haul the bike and FW at the same time.
Any dealer selling chassis cabs should have upfitters available. You will find Ford dealers have a better grasp on upfits - Most of their chassis cab offering will work with your Ram.