I've done many alt. swaps in the past. I always use the GM alt. I've installed them in old military Jeeps, boats ans when I rebuilt my forklift the stealer wanted $600. For an alt. so I installed a rebuilt GM alt in it for $120. and it works great.
Here's some info.
Delco 12-SI: The Delco 12-SI alternator, introduced around 1983, was a replacement for the 10-SI. The 12-SI alternator has the same outside dimensions as the 10-SI and will fit in place of a 10-SI without modification.
The 12-SI improvements over the older 10-SI model include:
6 large cooling holes at back for better cooling of rectifier, stator and other internal components ;
High volume axial turbo fan for greater air flow through the alternator;
Larger rectifier to handle more amps;
Wider stator and rotor for improved magnetism for better low-end output;
Increase in mass helps with heat dissipation.
The 12-SI alternators are available in 56, 66, 78-, and 94-amp versions.
http://www.google.ca/search?q=gm+al...Q&biw=1024&bih=672#biv=i|17;d|BFdLVccCdNv92M:
Here's how it looked on my forklift :
http://smg.photobucket.com/albums/v...iew¤t=wiring2-1.jpg&mediafilter=noflash