Edelbrock AVS2 Carb Dilemma

I contacted Edelbrock and they stated that the 1901 500 CFM AVS2 was correct for my application, and that the 1906 650 CFM AVS2 would be on on the large size for that engine combination. The Carb CFM Calculators I have viewed online show just slightly less than 500 required CFM for the mainly stock 318 at 6000 Max RPM @ 85% VE. I do not want to over Carb the Car, but I do not want to choke it down either. The Edelbrock LD4B Intake has such large runners considering the overall port size of the stock 1973 318 heads, and I thought this intake may be able to take advantage more with the 1906 650 CFM. The Groups thoughts? Thanks