The 65-66 C code CID decal normally would not have white/black checkered pattern, but only orange/black and just have '289 CUBIC INCHES'. This decal carries a C5ZF engineering number.
The A code CID decal was orange with black/white checkered patterns in the top corners and '4V /Premium Fuel' markings. This one also carries a C5ZF engineering number, but ends in 'D'.
Mike Murray's August '64 Dearborn A code coupe has the C code style decal. Maybe the premium fuel decals were not put into use yet then?