I am sure that it was a Custom Auto Sound radio I ran in my '67 many years ago, and they were designed like all aftermarket radios and fit at least satisfactorialy.
I sold it when I got the opportunity to pay much more for an original AM/FM, actually from a '66. With that, I can use a short range broadcaster and listen to my cell phone tunes.
My brother took an original AM from his '69 Riviera to a backyard electronics wiz who did automotive conversions. He modifiied it to put out 400 watts and added AM/FM to it. It still looked 100% original. He also offered usb and other inputs, although I don't remember him getting the additional inputs. I think that cost about $400.00 too. The guy was old then, and doesn't do it anymore.