The 240Z was popular enough that there were aftermarket kits to add A/C built & sold. There were also factory A/C cars in 1973 I believe. Contact the site sponsor AC Kits and ask if the aftermarket kits are still available. AC Kits was the originator of many aftermarket kits back in those years...

I've taken my car to 3 shops, all who have said it's too hard to get done and they weren't prepared to look at it. I know for a fact it can be done, as there's a few examples online, however I have not been able to find any suitable reading material, until I found this forum! It's a 1972 Datsun 240z...