So you are telling you do not what is the correct air cleaner decal? MCA must say what is right. One of them has to be right. And I am talking about what is sold in restoration catalogs.
First understand the frustrations but not everything is know and it takes time and effort to find and confirm many things. Because of this you may be able to "get by" with the incorrect one but if your intent is to find and use the correct one that is a different thing.
No MCA doesn't have to include those details and hasn't, in the past, in their rules or judging sheets. MCA and other clubs don't often identify the exact correct decal in most cases or incorrect ones. In general those details are seen as too numerous so they shy away from including in print differences between assembly plants or production periods for example. Do have gold winning Q codes with different cubic inch decals and none of them were deducted for the decal if your using MCA for a standard on this detail. Sure if you contact the Gold Card Judges for 69-70 Mustangs for MCA they will have their opinions. Was one for a number of years, years ago.
Yes one was correct just can't verify it with what I have in my resources.
Not all of the decals available are factory or correct. Often they are just what is available or something owners will buy so they keep making them. I asked about this 30 plus years ago to the oldest reproducers of the decals. I asked why he made, supplied and listed certain decals for an engine. His response was I make them because people buy them. My comment was they would buy the wrong stickers if you didn't sell them. In many of those cases the stickers/decals were not correct but "close enough" or just what was available. Efforts for some of the newer companies has been better but all can fall short only to surprise owners later on the judging field or elsewhere when the details are explained.