Sorry I have not gotten back to you sooner - Since your first post I have not had time to get out of town to my sister's farm and make the measurment of the pump's central casting. I shall be out there tomorrow morning and post the info for you tomorrow afternoon.
I'll get you the serial number of the tractor as well as the pump numbers - I don't know exactly what year it is, but judging from the grill it's a mid-sixties model.
We just rebuilt the carb in this tough old beauty and it would be a shame to let it sit idle for lack of hydraulics - your offer of assistance is greatly appreciated!

 - Robin