Sounds like the dual gear oil pump  is  an upgrade to the original single  gear pump.

something about  the input shaft bushing not stout enough,  getting  pounded out, and allowing excess oil to  leak out the  bearing- losing pressure-
   the upgrade uses a  larger bearing,  and  they had to move some stuff around to make it  fit.. or something to that effect.  the added  gear tells me they reversed the  direction of the pump.

does anyone know if the  old hardware is  the same for the new pump?