The standard size element being used on the Tbirds is 1/2"OD smaller than the factory original. I think the element might be for many of the Ford engines that got the enclosed units with the snorkel.
 I just think it looks terrible with the gap around the edge on the filter base. On top of that the ID is also larger(which you don't see) which would reduce the paper surface area that the engine can draw air through, possibly creating a restriction. 
I'm surprised there is no correct element for the early birds with the number of them still around. 
I have researched and found an air filter size that is 1/2" taller than stock but with the correct OD, though still with a larger ID than the original Tbird unit.
I spent last night playing with Playdoh in the workshop with a torch in the engine bay so I could see through the bulge grill. To my surprise most of the filter lid falls inside the hood bulge. The only places where it extends beyond the bulge are a small part of the radius to the left and right of the carburettor. The closest it gets is 15/16" away. In fact it would almost fit completely inside the bulge if not for the extended rim that they put on the Tbird filter lid. I'm not sure what reasoning was behind the extra lip on the outer edge. 
What are the thoughts out there on how close the air cleaner lid can get to the hood?