I suggest this top link. Easy to adjust, even on the move. Makes hooking up implements a breeze. Never had a problem with it rusting up on me. Philip.
For a while, I let my top link dangle with no implement on. I didn't realize the threads were getting banged up. I spent the time to clean up the threads with a file. Your's may need some thread cleaning. It doesn't take much to mess a thread up enough that you can turn it.
I have ground down the top link collar to get it to fit the tractor as well. No big deal.
I have one and it's pretty good but I don't think it has the full range of motion that the original top link has.
I find it harder to hook up implements since I cannot reach the control and guide it and adjust it at the same time. With my tractor, I have to walk around to get to the control. Hook up is a PITA.
And, of course, it requires an available hydraulic connection and is a LOT more expensive than even the Kubota replacement.
Ken
Doesn't your Kubota have a hook to hold the link up?