1965 and 1966 C body cars of the same body type that use sail panels in the interior will have the boards you need. Cars from hot dry climates will have panels that will likely turn to dust as soon as you try to extract them.
Yeah, they're nice, brittle, Arizona baked red plastic with a grain texture that matches the interior. My old '65 Sport Fury had the headliner that came down to the package tray like your's. Thanks anyway, Ross.. The hunt goes on...
Yeah, they're nice, brittle, Arizona baked red plastic with a grain texture that matches the interior. My old '65 Sport Fury had the headliner that came down to the package tray like your's. The hunt goes on...
My advice to you from my own experience (trying to find boards that are in good shape). is to recreate them with new material, using your old ones as templates. If you have a good one, and it's the wrong side, flip it over. I believe they're the same and can interchange.
Edit - I just re-read your post - plastic? I assume you're talking about the interior, and mine are under the headliner and are pressboard. That being said, I just did a search on google - are you referring to this type of molded panel with the interior light?
View attachment 443262
If so, then you're going to have a more difficult time, and I believe they're specific to that model. If they are what I described initially, then the other cars you mentioned in your post will have them.
Keep in mind that the 1/4 window shape on many 67-68 hard tops changed to the reverse slant, and only the fast tops have the traditionally shaped 1/4 glass, so only those will have the possibility of providing you with a sail panel. My google search did not reveal any plastic sail panels like your 66 300 has in a 67 or 68.
Good luck!