There are reproductions available. Most vendors have them.
Here's a quick video I shot for you with my AD.

https://photos.app.goo.gl/L7wGTb0Elld8ZWq03

The originals on the AD also have little "tangs" that are tacked onto the channel and interlock with the door frame. However, the repros I got from classic parts did not have these, hence the glue.
After you have reached this stage, the trim piece bolts on and secures it further for you.

Last edited by Fox; 11/16/2017 5:10 AM.
1970 Chevrolet C10
Grandpa's -- My first truck -- In progress to shiny
Follow the build in the Project Journal
1950 Chevrolet 1-Ton Dually
"Ole Red Girl"
In the Stovebolt Gallery
More pictures here
1951 GMC 9430 1 ton dually--Shiny! | 1972 Chevrolet C20- Rusty- the puzzle box lid for the C10 | 1962 AMC Rambler American- my wife's
Parts trucks-
1951 GMC 9300 | 1951-GMC 9430 | 1951- Chevrolet 1300