Nissan produced two different A13 engines: the 1974-only tall block A13 for the North America market, and the circa 1980-1982 A13 for asian markets. Additionally, bore-out A12s were used in racing in the 1300cc class and typically called A13 although they were in fact an A12 engine.
See:
Nissan A Engines: Overview | A10 | A12 | A12A | A13, old | A13, new | A14 | A15