Quote:All A series flywheels are NOT the same.
They are, however, dimentionally "interchangeable"

The A10 is the lightest, in stock form, but it is drilled for the smaller clutch that was used in the Datsun 1000 models
Next came the 1200 flywheel, & i suspect that later A12 flywheels are the same. This one was drilled to take the larger size clutch that was used on all subsequent models, so this flywheel is the lightest one to take this clutch size.
Next heaviest is the A14 flywheel. As engine sizes grew, so too did the flywheel weight.
The A15? I don't know about this one, but i "believe" that it is heavier again, but can't say for absolute sure.

Another spanner in the works is the commercial models, like Vanettes. I think that they might have heavier flywheels than the ones used behind the same size engine in a passenger car, but we would need to weigh known samples to be absolutely sure.

So there you go, they are NOT all the same as each oher.