Autolite 4300 CFM?

I have a 1970 Mach 1 351C 4V engine with a 4300 square bore carb. The carb was acquired second hand as a reman unit with no tag on it. It has the heater hose type choke spring which I believe was replaced with an electric choke in late 1970 or 1971. I understand the early 4300s (1967 or 68) were rated at 415CFM and the latter square bore units were 600 CFM. My engine is slightly beefed up over a stock 4V, i.e. a 600 CFM would probably be OK but 415 would be too small. Does anyone know how to ID this rating in the absence of the factory Ford carb tag? Thanks, BS