Originally Posted by Big Slick

can't think of anything besides the RTV. it's pretty simple in concept. i mean, the only thing sealing the holes in the cab roof is the foam gasket on the light. you can either

a) seal the holes up individually (i'm not sure that's even possible given the size of the hole where the harness comes through)

b) try to make your own gasket out of weather stripping commonly found at home improvement stores

or

c) run a bead of silicone around the gasket and call it a day.

A is probably too hard to do to make it worth the time, B probably wouldn't be that easy either since you'll have a seam to deal with that could leak. so C it is. i know RTV seams like a bubble gum and duct tape cure on your $40K truck, but it's better than having a leak.