Check out Carvana. I just bought a 2016 F150, FX4, supercab XLT, 2.6 L twin turbo eco boost . We were able to look at lots of different F150 on line and found one with less than 7,000 miles on the odometer. Looks new inside and out. Carvana does a complete detail, gives you the carafe, a 7 day no questions asked return policy and then 100 days or 4000 miles whichever comes first 50 deductible warranty. First time I used carvana and I was impressed, they handled everything. The truck was in Baltimore and I took delivery in Houston. I have no affiliation with Carvana, my local Ford dealer really didn't seem interested in doing the leg work to find what I wanted.
The truck was past Ford's 3yr/30,000, but I still get the 5yr/50,000. I think after the 4000 mile Carvana warranty I'll consider buying an extended warranty, as some mentioned, I'm a bit concerned about all the technology.
By the way, the truck has incredible speed off the line, the 2.6 L V6 twin turbo is no slouch.
Good luck truck shopping