What are these parts?

No question they are accessories for a mid-mount implement, most probably a mower deck. However, I suspect not KUBOTA.

The few Kubota belly mowers I've seen have an electric clutch and take the power directly from the engine. This one is clearly for a rear PTO.

The other assemby is for raising and lowering the mid-mount implement using the 3-point hitch. The engineering is very similar to the belly mower for my Massey 1010.