i'm in the market for a new-to-me 450 (11-16) and i can't make sense of the fluctuating gvwr. i've seen between 13.3k to 16k. of course i'd like to be on the high end of that range. what makes the difference? i thought it might be the 8 lug vs 10 lug wheels but that turned out to not be the case. looking at king ranch or lariat trim

 

From Ford 2014

http://www.ford.com/resources/ford/g...typu_sep11.pdf

 

there is a payload rating, a 5th wheel towing rating, a chasis hitch tow rating, and a different payload rating if you have the camper package.