One new EPC brand mechanical fuel pump (made in Slovenia), part number FP14441, 17010-N0200, 17010-N0225, 17010-N0227.  This fits:

Datsun 510 1600cc L16 1968 - 1973
Datsun 521 1600cc L16 1968 - 1973
Datsun 620 1600cc L16 1970 - 1973