What size carburetor should I be using LA 360 engine?

What size carburetor should I be using on my LA 360 engine? Right now I have a 670 Holley carburetor. It has a mild cam. The mechanic says the 670 carburetor is too small on my LA 360 engine. And it’s not getting enough gas in the engine. He said I need a 750 carburetor. Right now the car stalls out when I put it in gear.

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