Our 67 SS-350 was built in early April/67. Which emblem belongs in the center of the steering wheel and which emblem belongs on the gas cap?
From what we have seen, we believe that for your car's date, it would have had the SS emblems on the grill and gas cap. All of the SS-350 cars had the SS350 horn button, unless it had a optional wheel (N30 or N34). The N30 and N34 wheels had bow tie horn buttons.
Another thing to note is that no plane SS horn buttons were made from the factory. Big big block cars used the standard horn buttons.
Be carful at making conclusions from Chevys ad literature. For some reason it is not always accurate, especially for items like this.