Here's my design, that i'll be putting on my 84 XtraCab and my 87 Crewcab...it's a ram-air type, the downtube sticks into the ram head about 1/2"...when water-laden air enters, the water, being heavier, strikes the rear of the ram and, helped by the air pressure, 'weeps' out the holes drilled in the side of the ram, just behind the downtube.

The ram 'mouth' is rounded in the sketch...this can be done by stretching the mouth sideways after welding. The ram head is also mounted level, slightly above the windshield, to let water rivulets traveling up the glass run under it rather than into it. Mine will be aluminum tube and sheet, i just can't stand the 'ghetto' look...i need my stuff to look professional. The thin lines in the poor blueprint, done freehand in Microsoft Paint, indicate where and how the sheet will be bent.