Inliners International Forums General Discussion Engines Why isn't a 390cfm carb good for a 250 motor?

Nexxussian says "As I understand it the 500 Edelbrock / Carter, with the secondary air valve and the enhanced boosters on the primary side (compared to the 600) is supposed to be the hot setup (for a street 4 bbl)."

So what carb is this actually?