Size of the carb really depends on the RPM and size of the motor. For something mild to warm on the 302 size of thing would probabally work (500cfm). The really are a pain, and as I recall working on the AFB's more work then I had thought. I loved working on the old GM Quadrajet's but never really liked the AFB carbs for some reason. I would go with a single 4bbl and make an air box/filter that looks good, or scavange around for the webers, they show up now an again, but they require their own learning curve and are pricey.
Check around on ebay you can find some of the dual quads floating around now and again.
Sandy