We're in the market for a used f350. Found one online and trying to do as much before research as possible. From the pics and description, it's hard to tell. The truck appears to have a factory bed liner, so, we can't see what's underneath. How can we tell if the truck has the gooseneck prep package or not? Is there a way to tell if we look underneath? Was reading the Ford equipment for these trucks and can't tell if it's standard or not. Is it likely it's hiding underneath?

 

First off I have almost no experience with F250 and larger vehicles.

I would assume if the vehicle is set up with a gooseneck package it would include a trailer electrical connector in the bed. I would recommend finding a vehicle with the package and check if its got a connector in the bed or not, then see if the vehicle in question also has this connector.
I could be wrong but I do not believe that is a factory bed liner, I also would assume if it were factory there would be a cut out for the gooseneck ball mount.