Ah ! OK. I did not realize the 165 had such a low flow main hydraulic pump. I understand now.
On the inlet side to the PTO pump I'd see no reason why you couldn't just use the drain plug hole under the chassis. Get a plug that fits the threads, drill a hole through it and fabricate a hose connection to it. Or maybe get lucky and find pre-made parts that would work. Just a mess of spilled oil etc. when you go to change oil OR connect the pump.
On the return side , (if you have remotes) that provides a handy place to put in a "T" and run your PTO driven pump return back to the sump that way.
I don't have a 165 (An Uncle had one a while back & I knew some about it ...) so I cannot give you direct experience help.
If you don't have remotes, surely there is a plug somewhere with access back into the sump for the return. There almost has to be a plug that would have been used for the return from a remote.
For the return: This is really crude/ugly (and you probably would not want to do it) but worst case you could go into the sump via the hydraulic oil fill plug there on top of the transmission between your legs. Make/buy an adapter with threads to fit the fill plug hole.
Good luck and hopefully someone will come on with a clean solution.
