Quality marine pumps like the Jabsco and Johnson are expensive for a reason. The biggest is that they are ignition protected. Not a bad idea for a pump that mounted in the bilge area of a boat.
what are you trying to accomplish? If you need a replacement pump, just get the current Jabsco Ballast Puppy. If you need an impeller, I think all you need to really know is the first part of the model number.