The Holley model 2140 and 4000 are 4 barrel downdraft carburetors, called 'concentric' models by Holley. These are sometimes referred to as 'Teapots' because they consist of a throttle body assembly with a float bowl suspended above.
Famously, model 4000 carbs were used on the Thunderbird V-8s from 1955-1957, including the dual carb 1957 312.
Governed models (2140G and 4000G) were used on various heavy-duty truck applications, including IHC trucks into the 1970's.
Carburetor numbers were stamped on the rear of the base of the carbs, as well as appearing on tags. More information on Teapot carb numbers.