G'day DaButcher.
I would not fit a massey auxilliary pump,it would cost more than the tractor by the time you were finished finding and fitting the parts.
You would be better fitting a PTO driven hydraulic pump and running it independent from the tpl hydraulics that is take the oil supply from the tractor transmission housing to the pump ,from the pump to the Front end loader Dual spool valve and return via the transmission filler cap either drill and tap the cap three eighths npt and screw the return hose to the cap or Braze a fitting to the cap.
thepumps can be bought with the pto adapter already on the pump all you need to do is make a plate that utilises the pto guard bolts and secure the pump to that,easy, 3000 psi is enough pressure to lift anything I would not set the pressure any higher than that.
The pump only needs to be 10 to 12 gallons per minute with the standard Massey 20 loader ,or if you get a loader with bigger rams you may need a bit more flow but dont go overboard.
Happy Days.
Hutch.