A lot of kubota stuff is sealed by their liquid gasket only. The machining is precision enough that the liquid gasket is all that's needed. I think the part number for at one of the gaskets is 70000-73764. The service manual tells you which part # to use for which tractor and which parts are in question. When fiddling with parts that are sealed with liquid gasket, one must clean every speck of the old stuff off, and that includes the stuff that's IN the channels if the part(s) have a channel for the sealant. That's the worst part to me. I use a pick, some acetone (softens it up a little) and lots of patience. Then once all the old stuff is out, clean it up really well, including all of the oil residue...and when I am doing one, I like to make SURE that all of the oil is out of the cases so that it can't dribble out while the liquid gasket is being applied and part(s) reassembled.
If you do it that way, they'll never leak.
A good aftermarket liquid gasket is any of the Ultra silicones from Permatex. I like gray and black depending on the application but also copper for other higher heat applications. None have any offensive odors which is appealing to me since my nose is very sensitive. I like to paint the squished out sealants with the proper color paint after doing a reseal; makes for a more professional looking repair and if for some reason later on down the road the owner decides to sell or trade it, a potential buyer doesn't have to glare at a bead of squished out orange silicone and wonder what was done to it and why.