All the trucks should be prewired, but if you want them to function as factory you will need all the factory components. I believe that's just the fogs, a stalk with the fog switch and possibly adding a fuse or 2 to the engine bay fuse box. I think every SR5 I've seen has fogs already, weird that yours doesn't.
That said, if you are adding fogs, don't bother with the factory ones unless you're just doing it for looks. Their output is trash. I would highly recommend the Diode Dynamics Elites. Their output is tremendous.