Datsun - Nissan Carburetors
Datsun / Nissan applications generally use a  two barrel " down draft " style carburetor originally manufactured by Hitachi.

Although there are several different Hitachi designs used by Datsun, there are two designs used most often. The smaller casting style is used in most passenger autos where engines are usually 1.6 liter or smaller.

The larger casting style of Hitachi carburetor is used primarily in pickup trucks or other applications where  the engine requires larger barrel sizes.