CFM question Re Carbs and Chevies

So the only performance mods Im going to make to my vans engine noiw that Ive swapped a chevy into my dodge are intake, carb, and hei (its got points right now). Just a standard dual plane manifold will be fine, as the stock chevy 350 has enough power for what I need. A stock GM Hei will suffice as well. However, I am rather fond of edelbrock carbs and have had nothing but good luck with them. I usually put Edelbrock carbs on vehicles that I dont drive everyday because I dont really care too much about fuel economy, and they give decent performance. Now Ive been wondering what is the proper CFM for a 350 chevy? Should I run a 500 cfm 'brock on my van as this vehicle is my daily and I AM actually a little concerned with mpg? 1406-600cfm? Or? I dont want to starve the thing, but if I wanted tons of power and horrible gas mileage I'd just drive my 65 caddy lol.

Thanks rod! Once again, you are a lifesaver!