I think most people go for a carb that is too big. If your car is mostly stock or lightly modified 600-650 should be good.
I have a buddy with a 455 that makes 500+hp. His dyno session showed him pulling 689 cfm at 5500 rpm. He has a 950 Quickfuel.
Mine is 463 ci and a 500HP engine [dynoed] I put a 750 Holley on in place of the 800 and gained 10 HP and 10 FP. It's not just how much air will pass through but how well it supplies air and mixes the fuel at the needed ratios. Go to the Holley site and run their carb size calculator, my bet is they will suggest a carb under 700. Then again I could be wrong, wouldn't be the first time.