Here's a good link on the alternators that were used from 69ish and newer. Talks about clocking and differences in appearance, identification and amperage variations.
http://www.madelectrical.com/electricaltech/delcoremy.shtml
Bryan-NW 'burbs1972 MalibuVaguely stock appearing, and the opposite of restored.1999 std bore 5.7, Vortec heads, Holley Stealth Ram, GM cam700R4, Viking coilovers, 12 bolt 4.10 posi, and a whole bunch more