Considering that 80 percent (Ford marketing numbers) of 65-66 Mustangs had factory installed radios, yes. My first three Fords were ordered without radios as my uncle "could get a radio and antenna wholesale" (about $25.00, vs $60 from Ford - a Motorola). The block off plates were tossed, although I did keep a red 66 plate for several years (like, who knew).
Jim