'66 Rocker molding clips

Most of the clips are riveted on, 2 on each clip. The front and rear have large speed nuts that can be found in the wheelwheels. I use a large drill bit and cut off the heads of the rivets. Then I braze or mig weld the holes shut, then grind and fill any imperfections. Any perfections that won't clean up with a grinder would get a light coat of polyester body filler.

If you can't weld them you could probably tap the holes a little below the surface using a punch or a socket extension and then fill them. In this scenario I would first apply a little fiberglass type filler on the hole for waterproofing and then smooth the outer surface with a polyester body filler.