I mounted my antennas behind the cab on the bed rail. Look in pics. I dont have any of my radio at the moment but I used some epoxy and bondo and made a custom fit in the compartment where the ash tray goes. Works pretty nice. Ill take pictures today If I can.
In my old truck, I just mounted it on the top of the dash above the radio. To get the wire into the cab, there are grommets behind the drivers seat that will come out and expose a 3 inch hole and a smaller hole underneath it. Run the wire up through that and under the carpet.
On my crew cab, the grommets arent behind the drivers seat, but all the way in the back behind the second row seats. I Dont know about superduties, you might just have to go through the firewall or drill a hole in the floor somewhere.