dualies,
Jon is correct in that there is no "special" radio for a 68 CS, they are the standard optional 68 mustang radios. Also hcsstang is correct in that all 68 radios have the black push buttons, 67 are chrome. You could have the option of a AM, AM/FM, or AM/8-track. I have a pic at home I will attach when I get home.
Doug