I think the flanges on the 67 and 68 rear taillight panels were designed by Ford to ONLY hold the taillight harness in place on the back side of the taillight panel. I believe the rubber boots, of course, were installed to protect the harness from cut and scrape damage and consequently shorts.
The flanges are not involved with the installation of the cardboard luggage protectors. You will find that the REPO protectors are cut out around the flange areas so that the cardboard is able to SEAT UNDER THE UPPER LIP of the back side of your taillight panel. I found this to be true on my 68 KR which is an original, i say original car.
I have found, also, that if the installer pre-bends EASY the cardboard somewhat (use a hairdryer and a warm day) and has patience, your cardboard fits under that lip beautifully. TRY IT. YOU WILL LOVE IT.
All for now.
hicountrybob Bob Teets
what a site! Jon, we'll be talking.