Two (2) GM 12-bolt rear ends
One is 3.73, the other is numerically lower but I'm not sure what ratio it is.
6 on 5.5" bolt pattern
mounts for trailing arms (2WD truck donors)
panhard bar mount
IIRC, 62.5" WMS - WMS
no known trouble, personally put miles on the 3.73 with no problems, funny noises or the like.
$50 cash for both, and you must take both. I can post pictures later, but hey, if you don't know what a 12-bolt axle looks like, maybe you shouldn't be looking to buy one.