Do you already have a sharkfin antenna on your RV? It's a multi-band antenna, usually containing a cellular element, a GPS helical and a XM helical. I think they're powered as well, not sure if it's from 12v or the head unit.
The Ford head unit will likely want a Ford antenna, using some special connectors? Plus it'll want to talk to the body computer for steering wheel controls, transmission / vehicle in motion lockout, etc.
How about a Pioneer or Sony after-market head unit instead. Many of the in dash mount dvd / bluray units also have nav capability.
