I'm looking to change over my seadoo spline shaft to a Kawasaki drive coupling.

When I look at the part number it seems all the Kawasaki motors (2/4 stroke) use the same part number from as early as the 90s through to current.

Is that correct they all use the same ones through the different Engine's HP?

Also I see there are Billet aluminum ones around new. Are the standard ones cast aluminum?

Are the Billet aluminum that much better for standard use?

I would appreciate some advice on this before I buy the wrong thing.