I have the Thule square bar system for my F350, plus the Rhino-Rack T-Loader for the front as I have a front hitch on the frame. With a 6' you won't need that, just the roof rack. For piece of mind, I'd go ahead and buy the locks for the system as well.
2016 Montana 3790RD, Legacy Edition, G614s, TST TPMS
2008 Thor Vortex 26FS
2013 F350 DRW 6.7L 4x4, Edge CTS, B&W Companion, Viair 10007 Air System, Firestone Air Bags
2001 Excursion Limited 7.3L 4x4, V/B Springs
2001 Silverado 3500 DRW CCLB 8.1L/Allison 4x4