The lids that take a pie tin are shaped differently in the area around the wing nut.

I have an air cleaner from my old 76 Charger SE.(360 2-barrel) I also have an air cleaner from a 76 Newport.(400 4-barrel lean burn) The 400 lid was bent so I was going to swap it out with the 360 lid.(they are the same diameter) The "lean burn" pie tin does not fit on the 360 lid. It doesn't sit down flush because of how the wing nut area is shaped.