Hi, My 82 had a cardboard liner with a vinal headliner. I took a liner out of a 1992 removed the fabric and foam and sanded the cardboard. I then purchased new headliner fabric from an auto interior shop and used 3M super interior adhesive.
Diesel Brad is correct, the board is held up by the trim.
You can also find headliner material at some fabric stores. Her in CT we have Jo Ann Fabrics and they have some basic colors for a good price.
I also upgraded the suvisors to the 87 and up set up. Much more stable.
Good luck