Thanks to the suggestions of the oppo hive mind (borg really) I found a rebuild kit for an entire $18. I saved so much money I also ordered a set of metric S-K Flare nut wrenches.
JFTDC, this shit should be off the shelf. I’ve found NOS master cylinder for >$800 and a wildwood retrofit kit for $150, which one do you think I’m going to buy? Apparently nissan switched the position of the reservoirs from front to back between September 1970 and onward so my car has the old style and the other 500,000 Nissan Z cars made after that have the new style... The Wildwood kit seems like a great deal. I’m checking local auto parts stores too in case by accident they have one on the shelf. I am looking forward to a pedal that does not sink to the floor.
Larry Chen’s Datsun for your time.