Jay,
The SU (special utility) was built as a price fighter so it did not have the casting to mount the auxiliary valves.
There is a kidney shaped cover on the side of the transmission that has several drilled and tapped holes behind it - one has to be plugged with a specail plug available from your Kubota dealer. (There is a service bulletin on this)
Of the remaining two ports, one will supply fluid under pressure from the hitch pump and one is the return port. You can now supply an open center valve for auxiliary, loader, log splitter - whatever you need hydraulically.
Again, like Kenny says - go to the dealer and get the special plug part number from the service bulletin and you will be in business.
Good luck!