there should be 2 different tow ratings for the truck---one for conventional (bumper pull) & one for a 5th wheel
here's a link to a Ford towing guide on 06 models
https://www.fleet.ford.com/resources/ford/general/pdf/towingguides/2006RVguideApr08.pdf (maybe someone can make it a clicky)
2011 Ford F250 Lariat C/C 6.7 PSD w/Curt 20K Lb Hitch & rear Timbrens
2013 Chevy Tahoe LT 4x4
2013 Infinity 3860MS 5'er/15.5K GVW/41'
U.S. Navy 1978-1986