how much head flow to justify dually carbs?

i was always a firm believer in one big carb. but then i got into the really old stuff and multiple carbs are just common place, they didnt have 4 brls back then and liek jim said when they did they werent that big. i had a rover v8 for my coupe i never got to put it in but i set it up with 2 rochster 2g carbs on an offy intake i ran it on a test stand it it ran really good. had awsome throttle response and a nice idle. i was surprised how well it worked being only a 3.9l. i have since been thinking of a 2x4 setup for my dart, but i need to stop messing with it and just drive it.