How much is too much dual quad

My call to Edelbrock was about the biggest joke obtaining information on how to tune these carburetors. When I told the guy adout the two carburetors I had he told me that I couldn't use those. He highly recommended that I buy two new- I think it was 500 cfm's or something because that's what his coworker is running on his dual quads. I told him I'd been running those carbs for years now and I just needed help tuning them and he had nothing...