I also have a F-150. As a starting platform for a high quality audio system it is pretty good. Quiet in the cab straight from the factory. The door panels allow for some **** deep woofers. With the addition of MDF spacers, you could probably fit 4" deep woofers. Not kidding!
The spacing between the woofer and the tweeter is decent. There are even places to set the tweeter much higher on the door panel as well. The only problem becomes the distance between the woofer and the tweeter. Lots of people say spreading them apart is a no no.
The biggest draw back to the door panels on the F-150 is the grill that covers them. They are actually pretty restrictive and cover some of the area of the woofer. This cannot be good. I have beeen thinking about modifying these so they interefere less with the woofers. The next thing is unlike the Silverado, making door pods/panels is a PITA.
Are you going to dampen your doors? Trust me, it definately makes a difference.
Keep us informed as to how they sound in the stock locations.