Im not aware of any mower that has a different assembly you fit under the mower for the mulching process, just some sort of plug to make the deck into a 'bowl'.
Some dedicated mulcher mowers such as the Masport use a bar blade, i think the older Bolens ones do too.
Others use a disc with 4 blades on it and a plug.
Have you talked to Kubota?? They may have had options on that machine for mulching.
I think you might need the advice from someone well versed in mulching with mowers. Where it me, i would just make a plug and try it.
