Change up headliner

That's a tough one. I have never heard of a hard panel headliner ever being available for your car. Would have to be custom made. If I was to attempt this I would start with a panel out of a old van or something larger that could be cut down. It would have a slight crown built into it
which would be easier than starting with a flat sheet. The sails would be separate pieces.
It truly would be easier to install the factory replacements.
Do you have a cage in the way?