Towing capacity of a 2002 Ford F-150 with a Triton 5.4 l

this is a typical half ton truck. typical 5.4 liter truck engine will have 300ish HP and 300 ish torque which can typically move 17k pounds total on good roads. Uber safe towing capacity will be around 6,000 pounds (truck weighs another 6k) and the quality of your road, brakes and transmission along with whether the trailer has brakes or not will determine if you can go higher. Under the best of circumstances you will top out under 10,000 pounds and I would not take it much past 7,000 unless you really know what you are doing.

What is the length of my bed if I have 4 door and short box

I have a 2003 ford f/150 lariat king cab with 134k on it .tow package, runs perfect.

I haul pallets in my f150. Regularly do 5000-6000 lbs