My auto electric book from the 90's says buy alt / VR as a set so they "match". Does it matter ? They don't sell sets, and there's a generic photo of the VR's used for different makers and part numbers. I think I have a 60 amp alternator, all they seem to sell are 50 and 60 amp. Same alternator part numbers for 240, 260, and 280z.

Want to get a spare VR to keep in the car. Had both kind, mech. and elect., go belly up so don't know which. From the original look of the one on my car when I bought it, I guess they lasted longer previously. Maybe the new mechanical ones are made by older children, since they're more complicated. My new elect. one is working OK I guess. Test and adjustment per FSM for mech. type only, though.

I think the "set" reference means to always replace them both at the same time.  A failing alternator is likely to damage the voltage regulator and if you replace just the alternator, the badly regulated current will possibly take out the battery.

Yeah, my battery crapped out couple months ago, same time as the VR. Should have guessed the connection.

If you are still using an external VR, you can get these in Solid Sate models now, instead of Mechanical relay styles. The SS style are much more accurate and reliable. The SS models have an outside cover that is about half the height of the Mechanical relay types. I believe that Rock Auto has some Solid Sate models available.

1973 240Z . Rock Auto appears to have two solid state voltage regulators available.

AirTex Wells 1V1250 at $36.89 and AC Delco E661 at $49.79