If you hold the olds lens up to the ford lens you'll see it fits right inside of the ford, I drilled 2 small holes in the ford lens where the olds holes are and used a set of small self tapping screws and screwed them right over top of the stock fords. it worked fine they have been on the car forever.
My Olds 88 Tail lights that I have do not fit inside the Ford. They are about the same size. I guess I'll weld the old holes shut and drill new. Going to French the Olds Tail lights. So mounting the Inner light Socket in from inside.