I thought it was a Reese, not a Curt. Either way, there's a thread about it right now in the towing section you ought to look at. Evidently Ram has a couple of different mount points for the pucks and one is marginally wider than the other. The factory hitch doesn't allow for any adjustment, so the guy who started that thread sent it back and got a B&W, which does allow for that adjustment. Something to check out anyway. B&W seems to be the one most people like the best for the factory pucks, but if you already have a fifth wheel hitch you can also buy rail conversion kits that drop into the pucks and then you can mount any rail mount hitch. Might save you some bucks.
If you're buying a CTD Ram next I think that's a great move. I love mine whether I'm commuting to work, hauling the family on a road trip or towing my fifth wheel someplace. They're just awesome trucks and the Cummins is (just my opinion) in a class of it's own.