I pulled that number from a shaft on a previous conversion. Now there may be an updated part#. We give that # to our local kubota dealer and we get the shaft. I don't know if they have to cross it. Also it won't be listed under your kubota model so I wouldn't search using your specs. Try something newer '08 or so.
For what it's worth - the issue of spline wear - stub axle to hub - has been around in the automotive business for years. One manufacture (who only manufactures 4WD/AWD vehicles) recommends using Loctite 648 to repair the click/clunk noise typically heard when changing direction i.e. forward to reverse. 648 basically fills the void between the hub and stub axle splines thus minimising the wear. I have used this many times to cure this ill on vehicles a lot heavy and greater torque then the RTV's. Key to application is it must be spread on the splines. Unfortunately, you will have to disassemble the stub axle & hub to properly apply.