I bought an 88 that has the P/S setup run from the tractor hydraulics. It looks like a plumbers nightmare, but it works. I once thought of replumbing it, but feel &quot;if it ain't broke, don't fix it&quot;. 
I can look at it and give you the basics. That being said, seems to me someone said that the hyd system has more pressure (or volume???) than the steering motor can handle and will ruin it. Mine has a ball valve in one line, perhaps to restrict the flow to save the steering motor.