A wee bit of automobile history on the above "one size fits all" carburetor. These were an evolution as a result of the "cheap" customer.
If you look at "service" carburetors beginning in the 1930's, you find that, for the most part, a service carb was one for a later manufacturer/engine/transmission combination that had been slightly recalibrated for better performance than the original. This trend basically continued through the 1940's~early 1950's.
The first evolution of "service" carbs starting showing the carb for the auto transmission vehicles as also servicing the standard transmission vehicles (but not the reverse). This could be done, as the carbs for auto trans are calibrated richer to compensate for the fluid coupling losses in the torque converter. A vehicle with standard transmission would simply lose maybe 5~8 percent in fuel economy.
The second evolution is the multiple engine size as referenced above. This became "necessary" because of the proliferation of inventory. The parts house could not stock everything, and therefore the better products would be special order with shipping costs. By offering a product which will work (although less well than it could) on many products, the parts house could stock more coverage with less product, and because of the "economy of scale" the multi-displacement units could be sold cheaper.
Jon.
