I have been looking for the original carburetor for my car for many years. It’s the A.I.R. version for my 1967 Pontiac Firebird. It’s the California model for my MT, 4BL, 400. I have never seen the 5 digit part number (4456S) What is that? How do I know it’s the A.I.R version?

It is an original, round tag carb from May of '67, but has the 5 digit part number rather than the usual 7 digit number (7037273). So it's an early replacement. All of the casting and stamped numbers are the same as the -263 or -273 carbs.

Part numbers from the carb:

445S
7033883
70336C
32236 or 32226
29865
B37