In the video, he simply slides the rubber strip into the door and it is not held in by anything, but is free to slide up and down…he also identified the correct part, which is NOT the part that Classic Industries sent me- he said that the one I have will not work in these trucks. I am going to see if I can find the right strips.
At 19:15 minutes into the video, he discusses the strip:
Jerry Kassis Door DisAssembly - part 1