Schematics for the Ford F-150 can be viewed on the Ford Trucks website. Each schematic has to be individually searched for through the how-to articles posted on the Ford website. Another option to view schematics for older pickup trucks is Fordificiation.
As an example, the article explaining how to install a review camera contains the wiring schematic for the chassis's electrical system. It shows where to route the new wiring system for the addition accessory.
Schematics for older model Ford F-150s on the FORDificiation website include the wiring schematics range for 1967 Ford pickup trucks to 1972 models. The site features all types of trims and electrical systems.