For the cold air any of the above recomendations are good.
As for the hitch, I just went through that here. I wanted an OEM with a 2" reciever so I ordered one from the dealership here and it came 1 1/4". They said they dont sell any 2" for FX. :err: But you can get one on line for up to an '06 (which doesnt make a difference for '07, I'm not sure for '08 though). I ended up getting an after market one that sticks out more than OEM (I really needed a 2" receiver) but it was half the cost. I guess just make sure it's a 2"er.