What kind of setup is this???

So what were carburetors of this type usually installed on?

This type of carburetor, whether made by Zenith-Stromburg or by SU, was installed as factory equipment not only on numerous English, er, "cars", but also on Volvos and other non-English applications. Exact copies of the SU carburetor, made by Hitachi, were installed on Datsun Z-cars and others.