Bad Day, Very Bad day

Its a good idea to install the shaft early on in the build and measure its length out the bottom, from the pump mating surface. Compare that to the depth of the pump input from its mating surface.
The gear tooth design is causing downward force on the driver at all times. If there isn't a little clearance the pump will fail. As much as .100 before the shaft bottoms in the pump wont hurt anything.
We can blame some of these mis-match issues on aftermarket part sources.
Good luck with it.