I've been trying to figure this out for awhile, and I can not find how the water is getting in.
Here are a couple of pics of the result, and where I see the water collecting and dripping

I don't see any visible cracks, around the outside of the cab. The windshield appears to be water tight. I hit it with the hose and no leaks.
The water collects here at the front only when the truck is parked facing down a hill, like when I back it into my driveway.
Where is the EDIT water getting in!

 

Are you running your A/C?

 

I bet you the little drain on the front of the heater box is plugged..i had the same problem. it is a little rubber tube, bet ya thats the problem 4 sure.

 

I'm sorry, maybe the photos aren't very clear. The first one is of all the water in the floor, the other two are from the header where the sun visor mounts. The photos showing the hole are where the screw holding the plastic header trim mounts to. The water is dripping from the ceiling not coming in from the floor. It does this when it's parked in my driveway.

 

Maybe from your cargo light and running down the inner shell of the roof.

When does this water present itself, when it is raining, after you wash it?

Is the truck level when it happens or is it also on an angle meaning the street faces down hill?

 

Do you have cablights?

 

Any water stains on ther headliner? X2 on the lights, but I'd check the driprails around the top of the cab also. To check door seals, take a piece of chalk and "color" the entire sealing surface of the gasket, then close the door. When you open it, you should see a chalk line everywhere the seal touches. Any skinny parts can present a leak.

 

Thanks for replies please keep them coming.
No external cab lights.
How can it be coming from the cargo light? I thought that was all internal.
Yes the truck faces downhill when parked.
Yes after I soaked the top with water, but couldn't isolate where.
It's not from the doors as it is coming from the roof, and from the screw hole that the head liner screws into. So the water is between layers of sheet metal.
I don't think it's the external drip rails.
One of the first things I did was to flood the drip rails, and leave it for an hour, and no leaks.

 

Cargo light is outside facing the bed above rear window. They were optional. You could try taping off the door vents with blue masking tape, soaking the top in soapy water, and turn your fan on full blast. It's a long shot, but you might see bubbles where the leak is. That's sorta how some RV shops find water leaks. Only works if you can pressurize the cab.