I was purchasing a complete NOS ignition switch minus any keys. How difficult is to have keys made for it? Should I take it to a locksmith?

If you can get down to the tumbler cylinder, it should have a key code on it and you could order a key or a good locksmith could cut you a key if he has a proper blank.

You can also buy Datsun Z blank keys on Ebay.

Yes, take it a lock smith. If the core can be removed from the cylinder it isn't that difficult to make a key. Key blanks are common. I can't recall if the core is wafers or pins. Come to think of it, it's a double cut key, so it would be a wafer lock. To remove the core from the cylinder without a key, not a big deal to pick the lock. I have no idea what a lock smith would charge, but it's not a big deal. When I closed my business I kept all the key blanks, I probably have what you need. Jim