I recently looked over an '87 GTA that was flame red with red interior. Was the red interior available in all the GTA paint colors?

Yes, There was no specific exterior color that made a difference in choosing the Carmine cloth interior.

There's a maroon GTA on ebay right now with the red interior. I've never seen a red interior in a GTA, and although I hate it with the maroon exterior, it's definately very unique and quite rare. I'd love to have that red interior in a Gunmetal GTA.