pull the spacer off you dont need to run it on the alternator.. and the shaft should be long enough unless there is a keyway spacer or something else on it pull that off as well use the most of the space for the pulley it should fit no issues...

The water pump should just be the generic A series long nose water pump which means it has a smaller centre guide and gives positive offset.. at the moment you need to work out is it either a long nose water pump which is the smaller centre or the short nose water pump which is shorter and has a larger centre

I can take a picture of the differences to show you...

Or check this link and see the differences explained:
http://datsun1200.com/modules/mediawiki/index.php?title=Water_pump