my king ranch is rated at 8100 i believe with the 5.4 and 3.55 gears and those 20 inch rims. however i don't ever foreseen myself to be towing more than 6000lbs. i did once tow my 3900lbs 73 mustang 460 motor on a u-haul full trailer (2000 supposedly) and the car did have some stuff in it. so thats the heaviest load i ever see myself towing.

i am going to be towing a 20x10 u-haul trailer with about 2000lbs of furniture in it soon. so a total of mayb 3500lbs. i am expecting my f150 to be towing that weight with ease.