Hey, checkout this write up done by a performance magazine:
http://www.nissanperformancemag.com/september01/radcap.shtml
It makes sense.
I tried it and the cap fit perfect and only cost $10 Canadian for a non-Nissan part
Great bit of info 
I may sound like an idiot, but are all radiator caps the same size/diameter?
no.
Yeah I kinda thought so :rolleyes:
BTW I checked my GTR radiator cap, it has a bunch of Japanese writing on it, and says 0.9 bar at the bottom.
The Z32 cap may fit, I’ll have to try that out one of these days when I’m at a meet.
Aperantly all nissans of that era had the same size rad cap. So shouldn’t have a problem. But double checking never hurts either!
Good find, ill have to try that.