If you can rebuild your original pump, do it . They are the larger pump and are very simple and cheap to fix/maintain.
The later /smaller replacement pump did not have a slide seal between the pump housing and motor armature, so once they get clogged , they are in bad shape.
The original is also very easy to change brushes,the impeller is brass , so they have no plastic inner parts in the pump casing...this is a vane pump- nothing but an impeller, woodruff key and slide seal..simple as it gets.
These are high volume/low pressure pumps and they are the perfect match for the Bosch Injector pump .
You wll know the original pump as the wire terminals are toward the top of the armature casing, and the brush case has access screws. The later pump has the power therminals at the base.
The early ones also have a seal leak hose on the side to warn one if the slide seal is leaking without having to take the pump out..
KISS pump.. keep it if you can...