Welcome to the site.
Pushrods are readily available and were fitted to millions of engines. Nissan part number 13238-H1001
*
HGM Forklift parts - buy online
* Buy online -
Bprojects* Picknpull in Sparks has a 1979 Datsun 210. If it has the A12A engine it will have what you need. Don't bother to call, they are completely self-service and you can remove the parts yourself
Would I buy used pushrods? You betcha, it is rare for them to fail they usually last forever. Causes of failure include too tight an adjustment or severe pinging
A 1979 in California/Nevada should have the A12A engine, which is bigger than the A12
Check your engine compartment ID plate

So you have a Datsun 310? Can you post a photo of the wagon? We like photos

The one in Sparks is a Datsun 210 (B310) but uses the same engine type as a Datsun 310. But if it has A14/A15 then the pushrods won't fit the A12A