Oh well I may as well jump into this discussion with a few ideas of my own about carburetion engine size combinations.

I read from the above posts that 1 carburetor can cover a broad range of engine sizes. That is true up to a point with vacume secondaries. The primaries are directly hooked to the accellerator pedal and regulate engine speed and load. The secondaries are sensitive to engine load and vacume only and will only open as much to flow enough air fuel mix as the engine demands. Okay everybody knows this. What I want to add is the term Air velocity through the venturie. We are taught that air flowing through a tube that crimps down accelerates though the smaller opening. This increase in velocity also creates a pressure drop at this point. Now it stands to reason if we increase the velocity by using a smaller venturi, the preasure drop is more pronounced . You can only get away with this up to a point, because you cause a flow restriction. Now this is why different size carburetors have different size venturi and throttle bore combinations. Because they are desined to give optimum best flow at certain airflow velocities. Notice that I said airflow velocity and not engine size or speed. The engine size and speed determine the airflow velocity through the carb. You get tochoose where you want the carb to run most efficiently in the engine power range by choosing different carbs springs and jet size.
I like to think as vacume secondary carbs as a pair of elastic waistband pants one lengh size will fit a number of different abdominal shapes but will get the job done without the expense of going to a custom made pair.