Something adjustable would be okay. Whats on there now is a big old oil bath type air cleaner-original but takes up a lot of space. It has an adjustable collar-when you put it on the carb, you must turn a long handled screw type arrangement that tightens it up so no air can get by it.

Even if I could find an adjustable paper filter that would adjust down to 2 1/4", that would be great.

The car in the picture is a 1950 Dodge. I imagine most Mopars of the era would be about the same.