Ime trying to get parts to do alternator upgrade on my 77 280z, but the auto parts stores around here are telling me that the only 70 amp alternator they can get is from an 84 300zx. They also tell me that all alternators made for 280z and 280zx are all only 60 amp. even the turbo cars. Arent the turbo cars suppossed to be equipped with 70 amp alternators. I would like to upgrade to get away from the voltage regulator, and I would also like to find 70 amp alternator, as I have a 2000 watt dual amps pushing 2 15 inch subs, and 2  1500 watt 6 x 9 kenwood 4 ways,and 2 piezo tweeteers, so Ime thinking I should run something a little heavier than the stock set up. I do have a 1200 watt digital power capacitor to help with power fluctuations due to deep or prolonged bass notes,but I listen to classic rock and not rap so that helps. So any ideas on alternator issue? Thanks muchly.

The Nissan 70 amp alt. is NLA from Nissan and the parts rebuilders just make everything 60 amps.  So there is no 70 amp available.  

 

You can change the pulley, and shave the case, and rewire a 90 amp 90's year Maxima alternator and it will bolt in to the brackets.  It takes some effort but it works.  

 

Or you can go with one of the super-duper alternators here:

 

http://www.datsunstore.com/advanced_search_result.php?keywords=alternator&osCsid=856ee9bb129c2155c9dd2874e96c12c6&x=0&y=0

 

By upgrade you probably mean getting rid of the external regulator.  The last link is a "one-wire" setup.  The Maxima alt. will require some modifications at the old plug.