[FWB]

on a ford small block there are a wide and varied flavors of intakes to choose so the different carbs can be used also on ford big blocks fe's and 460's alike there aren't alot of players in the intake market especially dual planes for the street. if a person was to run a vacuum secondary carb, there are only a few choices and those choices get slimmer based on the motor you have. the combustion engine is a air pump, generally the more air you can stuff through it the better it will perform. that is usable air. if there is no performance reason to run two carbs why would anyone run fuel injection. the bigger air flow shouldn't do anything for performance.
two carbs is worth 5 tenths at the track, period. two carbs are easier to feed than one. you can achieve more hp gain for the street without sacrificing drivability