Datsun 1200 uses a traditional type of flywheel at the back of the engine. The face matches the Clutch while a ring gear is attached to the perimeter for the Starting Motor to turn the engine.
All flywheels for A-series engines interchange -- for rear-wheel drive vehicles. The A12 flywheel weighs a bit less is the main difference.
In 1974 flywheel bolts changed from British Threads to Metric threads. So the bolts are not interchangeable from early to late.