72 and later marker light welts?

Based on what my quaterpanels looked like around the marker lights on my 75 before I restored it, water definitely got in past the foam gasket. There was surface rust around the three holes on each side of the metal, even on the front fenders around the yellow side marker lights. I put a bead of caulk around the back side of the plastic marker lights, let it dry and then attached them to the car.