Yet ANOTHER Mystery Part

The adventure of putting a '66 Barracuda continues. Again, in my defense, I didn't take this car apart. Please look at the attached picture (from my other '66) & you'll barely see the outer edge of a shiny "L" shaped piece that tucks between the headliner & the rear window seal. These pieces that came with the car that I'm putting together were both broken. They're a hard...and VERY brittle plastic. Since they're both broken, the gap is EXTREMELY tight & I can't imagine what the hell they do (except a very minor cosmetic improvement), I'm inclined to ignore them, and put them in the 'more trouble than they're worth' category and moving on without them.
Why were they there in the first place? Am I making a mistake? If so, how big? :)

Mystery part.jpg