Crusty,
If your springs are good and the plate is not warped, that will be your easiest and most cost effective route short of a very lucky find on the internet. Allowing you to go look for other parts.
If you don't have the factory owners and factory parts manuals for the 320, visit the NICO link pasted here and click the 320 tab. I've downloaded and printed both out years ago. Very helpful when tinkering time comes around. Also might want to visit the NICO forum for the 320. Don't believe there's much activity there anymore, but a good amount of info to be gleaned. If U visit the 320 forum, be sure to check out the posts by 'Lil Truckie'.
https://www.nicoclub.com/datsun-service-manuals