For street use, I recommend "regular" oil and lubricants. For the CA18, check the owner's manual. It probably takes 10W40 oil.
For the gearbox and diff, 90W should work, again check the owner's manual. For the Datsun 1200, Nissan recommended (in 1972) to use
75W to 140W, so today's common 75W-140 should be perfect.
I buy whatever brand is on sale and meets Nissan's recommendations. I've never had an engine break, over 26 years of driving and many vehicles brands.
For the Datsun 1200 stock engine, transmission and diff, Nissan recommended many lubricant brands by name, and those same types are still commonly used 35 years later (example: 10W40).

Nissan Recommend Lubricants
For the radiator use distilled water in a 50/50 mix of coolant/antifreeze. If you live in freezing areas, check the coolant container for instructions (may require a 30/70 mix in very cold areas).
More details:
Coolant