5300 3rd scv valve addition

I just bought a 5300 that has the joystick connected to two valves that operate the loader. I'd like to add a 3rd valve kit, but the parts person (as well as one of the owners) at my local JD dealer say there is no option for that. I want to add the 3rd valve to operate a hydraulic top link or other rear uses. They said that there was either zero or two valves possible on the 5300, but not three. I've seen pictures of three sets of hose connections on this series tractor I think, but am not sure if it was a 5300. If anyone has added the 3rd valve kit to a 5300 or devised a way to get remote hydraulic power at the rear other than disconnecting one of the loader circuits, I'd like to know the part number of that kit. Thanks, Steve
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