So today I looked underneath my truck and there's tons of rust, drive shaft is completely rusted, differential, front bottom engine bay. I need the under carrige recoated. Does anyone know shops in Bay area, ca? When I bought the car it was always in the Ca. First oe probably took it in the snow.

 

This is a very common observation across the entire F-Series line-up. The surface rust acts like a patina. You will see body panels rust out/through long before any structural damage would happen to the frame or drivetrain. If you do some searching here & elsewhere, you will find tons of threads regarding this "issue."

 

Mine is rusted in the same places, I'm going to hit it with a can of black spray paint one of these days..

 

Fluid film! I coat the under-carriage of all of mine each year. If you're not in the road salt much you probably could get away with doing it less often.