The diameters I gave were of the air horn on the carbs. The outside diameter of the surface which accepts the air cleaner would probably be about 1/2" larger.
I believe the QJ became the only choice by '67 but there were some put on earlier. I'm taking a shot in the dark here working from distant memory but I think if the air cleaner has a base plate that goes on the carb and the cover has the snorkel it's for a Carter. If the main body of the air cleaner goes on the carb with just a cover then those are the ones that work with the QJ. - Bill
Buick started using the Q-Jet in 66. That year I have come across 2 styles that fit the Q-Jet. One is from a 66 GS Riviera or WIldcat (also a very rare GS)
The other looks exactly like the 65 AFB style but has the larger diameter carb inlet and the air intake horn points to passenger front vs 65 that points to driver side front.
I have 2 of these, one chrome plated and one plain black.