273 Carb Size

Keep in mind that the AFB's had an air door which made them operate as a quasi vacuum secondary. This is different than the upper door on the newer AVS but it has some of the same effects. This means they could be somewhat oversize and still work fine.

Also realize that different carb manufacturers (Holley vs Carter) measure carb airflow DIFFERENTLY and in fact, Holley measures 2bbl carbs different than 4bbl carbs. As I recall, 4bbl Holley were measured at 1.5"Hg "drop" and 2bbls were at 3"Hg. This means that 2bbls "seem" higher flow than they actually are, AKA if they were measured at the lower drop as the 4bbls, and thus compared directly, they would come up lower flow numbers

Also, some brands flow "wet" (I think Carter) and Holley flowed dry, which makes a tremendous difference in readings