I have a 60 gal RDS and a Bak Fip fold up cover. The cover sits above the rails when folded up and towing and never had an issue. I have 24,00 miles on this fiver and I had about 5,000 on previous fiver with this combo. We full time and have traveled most of the lower 48. Your issue will be with the tool box part as that may add 6 in or so over the rails. Have you checked into wheel well tool boxes as an alternative? Anyway with my 60 gals I fill up a whole lot less then I did without it. I have 50,000 on the truck. Measure the distance to the hitch legs you probably have enough room. Anyway measure twice order once. The aux. tank is a well worth the effort unless you like filling up everyday and not saving money.
