Well, if you use a 4 barrel carb, you might want to use something kind of small like the Holley 450 cfm. The two Holley/Webber carbs at 230 cfm each add up to 460 cfm, so the flow is about the same, theoretically.
What you might notice with two carbs though is that each carb is spaced out more so that you probably have a little bit more of an even flow of air/fuel mixture to each cylinder, whereas the single 4 barrel would still tend to make the center cylinders run rich and the outer cylinders run lean.
My altitude is very high though, (about 5800 feet) so I'm thinking that for me, twin carbs would be overcarburetion. If I were at lower altitude, I'd probably prefer the twin carbs.
