Was talking to a gentleman at one of the larger Nissan parts suppliers today.
Their site doesn't go back to anything earlier than '84.
He gave me the name for a website that specializes in early Datsun/Nissan parts that are not listed on the site.
The site is http://www.carpartsmanual.com/#ManualsMenu
It's pretty extensive and it has Nissan part numbers.
Fantastic resource for us early Z car and Datsun restorers.
joe