Just need a correct new heater nipple for your 2L water pump?  Don't want to spend 38$ on one fitting?  These last about 50 years.
 
Here you go....
 
Nissan or Aftermarket depending on inventory.  Correct Nissan threads of course  (these are NOT NPT hardware)   
 
Also fits the rear of the SU intake manifold and solex water tube.