DD, I am sure someone will beat me to the punch, but I just bought three Duster parts cars. When I start to dismantle I will let you know what I see. I pulled down the cardboard one out of the Demon and small c-shaped clips held the liner to the backboard. It all snugged up under the roof line trim. The C Pillar or Sail portion was separate. Mine was disintegrating so I trashed it. I found some ABS replacements, but I can't tell you about quality or fit, not there yet.
I'm thinking the car had a cloth 4 bow headliner. like I said the bows were in the trunk and there was a cardboard liner up there but no fabric glued to it, so it must have been on the bows. I cant figure what the bows attached to. The car did have upgraded dash trim so if you could get a fabric headliner on bows maybe this car had one..