I have no idea! I shall have to look. If you can reach the rail with a pop-rivet tool, it should be possible to replace the rivets with short pop-rivets.
I do know that the remove them by drilling you have to remove the frame -- big job, the headliner has to be completely removed.
I'll take a look-see on my way out to mow grass!
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!