I need to replace my alternator. I have a 1972 240z built 6/72. According to my ZCD, the correct part number should be 23100-P0102(R - all now are rebuilt), which indicates a 12V-50A Hitachi LT150-05B. However, Courtesy Nissan shipped me a P0103R (Hitachi LT150-10R). To further confuse things, I am told the part number I should look for is 23100-U5800R or -H6206R.

Exactly which is correct??!

I'm not well versed on part #'s but I will share this.The LT150-10 is a 37.5 amp.I assume the "R" means reconditioned.The 260z used a lt160-23 that was 45 amp.Due to more electricial requirements on a 280z it used I think a 50amp.That may be the 50a unit you mentioned.Any of those will work for you.The main thing is make sure it uses external voltage regulator,unlike the 280zx and up units.Odds are yours only needs brushes.Two screws hold them in where your wire connector plugs in.Thats the neat thing about the nissan units is you can replace the brushes cheap and easy while on the car. Have fun!!! Daniel P.S. the 50a/280z is what I have been using since the 80's