How bad are the floors? Are they rusted the whole way down? Typically the area that is raised a bit for the seat doesn't rust out. I had a 66 Mustang where that middle part was ok but the rest in the front and back were all rusted out. I made patches and welded them in and it was fine. That's most likely what you'll have to end up doing because I don't think there is anyone out there making reproduction floor pieces like for other cars like Mustangs, Firebirds and Camaros, etc. I would use galvanized steel myself.