The air cleaner decal for the M code 351C 4bl is orange and black and did specify"Premium Fuel." My first 351 C-powered vehicle was a '70 M code Torino GT. It had an orange and black air cleaner decal, the same as my '71 M code Mach 1. The lid and air cleaner housing was Ford blue.
Ford released the chrome air cleaner lid with the blue and white decals at the start of the '72 model year. Two of the three '72 Gran Torino Sports I've owned were Q codes and had chrome lids with blue and white decals and specified regular fuel. Depending on when built, the '72 model-year lid label would indicate 351-CJ or the later 351-4V. The 351-4V designation would continue through the 1974 model year as Ford built the final 351 C's.
Ram air, which was standard on the Boss and optional on other models, did not have any decal on it other than the '71 Autolite or the '72/ Motorcraft service label on the left front of the housing. There was never any decal or label on the lid. Unless showing your vehicle at a Concours level, you should be able to proclaim whatever you want on it. I felt that they always looked like something was missing with nothing on the air cleaner lid. A popular decal many use is the "351 C.I.D. Ram Air" from the '69-70 GT-350 Shelby.
There is a three-piece decal set by Osborn Reproductions sold by all the Mustang vendors. It's listed for the '71 model year ram air and seems to be another product of more incorrect vehicle application. As someone who has been around long enough to witness these cars being unloaded off the Motor Convoy trucks, I have never seen any ram air housings with any more than the Autolite or Motorcraft service decals. A smaller decal in the Osborn set states, "Use Air Filter Element A171C. That part number is the format for an AC Delco part number which is the service part division of GM, much like Autolite/Motorcraft is to Ford. The A171C is also the same as Motorcraft FA-17. Both of these part numbers are for competitive make vehicles. The application is for '60s Chrysler, Dodge, and Plymouth vehicles.
I can assure you that Ford and GM were not sleeping bag buddies, and Ford would not suggest a GM/Delco replacement part for any of their Ford Lincoln/Mercury products!
