I have done it the one piece head liners. It took three to get it right. I'm going to have to do another one for my new '39 project. I did save the one that was in there and am thinking of an elaborate plan to salvage it. It would be worth the time I think. If you do buy a new cardboard one don't get it too wet. Start from the back. Then the front. Then the sides. I let mine sit damp in a plastic bag over night. Have a helper. Put the trim pieces on first on the back. Leave a big space between the screws and trim. Then you see the holes have slots. You slide it between the trim and get it just right and start screwing the back trim tight. But make sure its square. The next time I will make a prop to help hold it up. Like we use for dry wall. Basically a big TEE. Good luck.
