Are you going to use longer gears in the pump or a new gear/rotor design? In the foggy remains of my rapidly dimming mind I recall a tractor or some heavy equipment pump that they used a Blanchard ground and pin located <> 1/2" spacer and longer bolts so longer gears could be used to give more volume. With the whiz-bang kids now they could just make up some 3D printed patterns to make a new mold to give a longer housing---probably quicker than it took me to type it out. A spacer plate could be plasma/laser/water cut quicker than what it would take an old fart to set up a mill. IIRC the gear bores in the housing are just overlapping circles so machining the new spacer wouldn't be complex. I used to love speed, now I'm getting to hate it.
