The only extended warranty worth a plugged nickle is the Ford Extended Service Plan (ESP) sold by Ford and Ford dealers. Don't even think about buying any other extended warranty.
Which plan do you want? Note there are five different plans, and they can be customized.
https://www.genuineservice.com/esp/plandetails.do
Which plan can you pay for? The more they cover and the longer they cover them, then the higher the price. They even have one that covers almost everything almost forever, but nobody can afford it.
https://www.genuineservice.com/esp/home.do
Click on the "purchase" button and follow your nose until you know the price of the plan you want. But don't finish the transaction. Write down the details of the ESP you plan to buy, then "shop around" to Ford dealers for the best price. (Just like you shop dealers for the price of the new truck.) Your Ford ESP is good at any Ford dealership, not just the one you bought it from.
One place to include in your shopping is my dealer. He has sold dozens of ESPs to members of TheDieselStop because he doesn't try to get rich on each one. Call Danny Ireton at 1-432-756-3321 or 1-800-953-3321 and ask him for a quote on your ESP. You'll probably buy it from him. You won't be talking to a flunky. Danny is the dealer and his mom is the owner of a small Ford dealership.
Just remember that the ESP has the same restrictions as the Ford bumper-to-bumper warranty and the diesel engine warranty - no mods allowed that don't meet Ford specs.