Correct about it being a 550 frame, but there are mods to make it RV ready.
One biggy is frame extensions to gain the length for the motorhome. On my previous F53 chassis those extensions required additional support to allow for the added capacity of a class IV hitch. Those extensions are the weak link, but can be reinforced to work by a good frame shop.
It's not quite as simple as just adding a bigger hitch unless the frame is already up to the task.
I have to say, once my rig was set up with the class IV, I never looked back. It's nice to 'not worry' about the little things.