Aircooled VW South Africa

I am busy ordering parts for my 1970 baywindow that I
want to take to Sanie.
Not so familiar with these later model cars and engines.

What would the correct oil pump be for a 1600 bus engine? 21 or 26mm? The 21mm pump is available in nos
from many suppliers, but not the 26mm.
The 26mm from Shadek is available all over and Febi at some shops.

Will the 3 rivet cam and 21mm pump do the job, or the
4 rivet with 26mm?

21mm for single relief case, 26mm for dual

Schadeck is a good pump, I use them on my engines