If your going to tap into the hydraulics you'll need a power beyond valve and tap into the lines by the valves now to power it, the pto was supposed to be to power a winch or backhoe attachment, you put a pump right on the pto and ran it that way, while the machine was in gear or in neutral the pto ran, only one direction at all times not reversible. If your running something continuous then go with a pto pump like for a backhoe attachment but if its to run a cylinder or something like that just put a valve on it and tap into your lines to power the valve to add extra valves on your dozer, to run a hydraulic motor and to reverse that its no different than any other valve just push the lever the other way, with a pto pump you'll need a valve installed off of that as well so either way your putting on another valve. The winch and backhoe had valve bodies installed right on them as a unit along with a pto pump and you plumbed into the return line under your tank and also into the supply line under the tank to get oil to feed the pump, some even had their own tanks build into the system and all you did was hook up the pump, seen them both ways over the years
The current system on that dozer should be open center system hydraulics, can't recall off hand what the volume is maybe around 20 gpm and 2500 psi but don't quote me on that for sure, just what I was recalling from memory.
