not sure on the hinges, but Chevy would be the same if you haven't checked that way - the starter hole plug wasn't much used before they invented a different way to start the engine, so no factory original to reproduce, but if you look someplace that has a good array of electrical supplies, there are a range of 'blank out plugs' for electrical boxes and one of those should fit - just silicone it in and put the mat over it and no one will ever know
Bill