Those kiwis are pretty resourceful especially when you
compare how little population & $$ they have vs Australia.
Im pretty sure they were ca20e or z20 valves both 42mm stock
as the bottom of my ca20 valves had the same nissan insignia
and measured 42mm in diameter as do some Z inlet valves.

http://datsun1200.com/modules/myalbum/photo.php?lid=20264



42mm in could be the ticket as you dont need anything but
standard valves for exhausts for turbo.
Yet A14force could have benefitted with 40mm inlets and
34mm ex as supercharging needs a bit more ex flow.

These are the CB vw heads that can make 180+ HP for 1.7L engines
https://www.cbperformance.com/product-p/1409.htm
You will notice how nicely shaped the chambers are to suit
the massive bores avail to VW engines while the Kiwi head
above is like a squashed up version but pays attention to
make sure that big 42mm valve stay more central in the
cylinder chamber to keep the charge away from the cylinder
walls with no notching on top of deck required which is
what you want to maximise a deep compact tornado effect
centered in the cylinder away from walls a very clever design.