We tow a Safari 27'FB Special Edition with an '05 F-150 5.4l (to my knowledge, there is no difference in the engine between mine and the newer ones. The BIG change came from '03 to '04 when they went with the 3 valves/cylinder giving a huge boost in both HP and Torque).
Last summer, did a 3900 mile trip without a hiccup from the truck. Just be prepared for the gas mileage.
Loaded truck and partially loaded trailer: Using AC = 10.5 mpg
Loaded truck and partially loaded trailer: not using AC = 12-13 mpg
2005 F-150 5.4L Supercab 4X4 (Betsy 3)
2008 Safari 27FB SE (Arvin as in RV'ing)
2010 TREK 2.3
Fair is where they put ribbons on pigs.