I finally found my "red rubber inset" material. I was hoping for a vendor part number on it, but nothing. All I remember is I bought it at a hobby supply store. It's has a stick back side. I used it on the 65-66 gas cap cable (a loop design) nut, 380331-S8, 12-24hex lock nut (AMK Guide To Ford Fasteners, pg 195). The holes on the red sheet show I used a 9/16 punch.
Jim