For low cost projects, a correct 1/2 year 1600 pump

Shaft protrudes thru the metal 4-blade fan per 67.5  
 
Fan fasteners included.
 
Can also be use on 65-67 blocks if you change the lower stud and fan.
 
Avoid Ebay, there is all kinds of incorrect pumps out there!
 
This pump uses a stamped impeller (as do most modern water pumps).  If you want the cast impeller pump, here it is:  
 
Water Pump 67.5 1600 | datsunrestoration (datsunrestorationproducts.com)