Kubota B21TLB (B21, TL421, BT751) Toyota SDK4, T116 Bobcat
Exploded parts diagram available from kubota http://www.kubota.com/part/partsList.aspx
Since you have hydraulics already on the tractor, have you considered using them, you may need an extra relief valve etc, but if you can plumb it in, it saves extra pump etc.
EDIT: Looking at the parts diagrams it "appears" that your valves have a relief valve built in, adjustable via shim thickness. (I could be wrong though)
Found this thread, some specs in it, and he has done similar. K-650 is same as L-650 it appears. http://www.tractorbynet.com/forums/hydraulics/128319-kubota-backhoe-powered-rear-remotes.html