The early '63s used a Wonderbar and then the AM/FM came along. I don't know how to tell the difference in Midyear radios or if there is a difference. First I would look in the yellow pages for an auto radio rapair shop and have it checked to see if it works. Then I'd go to
Hemmings Motor News online and search the Corvette Parts classifieds for radios to see what others are asking. You will probably find more for sale there than in any other Corvette Classifieds. Also you could call some Corvette parts vendors and see what they are asking. Check the Portal (click on "Portal" tab above) to search for vendors.
Tom