Kubota makes it tuff to "redneck engineer" thier tractors.

You just about have to use thier valves. I have a
L4740 with two dealer installed remote valves. On my tractor, there is a plate on top of the lift cap that covers the remote valve pressure ports. To add the valves, this plate is removed and another plate (part 010 in the pdf file, which is part of the first valve kit) with the pressure lines is attached in it's place. These pressure lines bring the fluid to the remotes. Your first remote that you buy should be the most expensive one. The reason is because this mounting plate that I mentioned, the inlet, and the outlet is included. With the 2nd and 3rd valves, you do not need addtional plates, inlets and outlets, therfore they should be cheaper. The valves just stack beside each other. I would say that you should be able to get all three for around $1000.00
The only other option that you have is to find a place to insert what is called a "Power Beyond". However, you will need to tap into the pressure line somewhere and tap into the return line somewhere. If you decide to do this and not go with the factory valves, I suggest that you go with Prince stack valves. The reason is becasue if you ever want to add more valves, all you have to do is buy the valve section and another bolt kit to bolt them together. For example, if you want two valves now, you would buy a inlet, two valves, an outlet, a two valve bolt valve kit, the hoses, and quick couplings. However, if you want to add a third one, all you do is remove the bolts, add another valve, and a three valve bolt kit. I think you can add up to 10 valves together, and the prince valves are easially avaliable. The stack valves that Kubota uses are not made by Kubota, but I cannot figure out who made the ones on my tractor.
I attached a PDF file with the parts breakdown of the valves for my tractor. I hope this helps.