Have you looked into the transferflow replacement tanks ?
Mine is a short bed but Ive got the 50 gallon tank in stock location and no problems with the OUO traction blocks I run.
Id guess it would be the same for your application also
On this same topic does the tank hang down that far on a 08-10 and would the aftermarket tank for a 08-10 work on the 11 up? If I removed my urea tank, I was wondering if it would work.