I recently spent a day installing my new headliner, not the easiest of jobs on the AD. There was some discussion about the headliners not fitting. First I bought mine from ClassicParts.com a while back and it was stored on a bench so it would flatten out in the middle and the ends could still curve. Next I saved the early style (1947-48) center bow from a parts truck that uses the screw on center piece it looks like this.
https://www.flickr.com/photos/advance-design_parts_co/18770380205/in/album-72157631867396207/
Since I was using this style I ordered the early matching headliner. I had read that some others are short but this early one installed in this way I actually had to trim in a couple spots. Anyway a job I have been dreading worked out pretty well.
https://www.flickr.com/photos/advance-design_parts_co/18149693683/in/album-72157631867396207/
The interior bracket above the door controls this signal arm (from a 2-ton farm parts truck).
https://www.flickr.com/photos/advance-design_parts_co/18772877171/in/album-72157631867396207/

1950 Chevrolet 3/4-Ton 3600
More pictures on Flickr