AFB with vacuum secondaries

Found something today, I didn't know existed. A carter afb with vacuum secondaries. It's from a 1957 ford fair lane with a 312 engine. Carb is in overall good condition. Got a kit coming from Napa for half of what the carb doctor wanted. The vacuum diaphragm is a little harder to fing and almost as much as the carb doctor kit.

Any body know anything about these carbs. Anything on cfm, reliability?

Numbers is a 2441sa

Keith:)