I can see some numbers stamped into the case. Those might help identify it if you don't think it is stock. 3.54 was a stock ratio for the Dana 44 in a GMC. GMC also offered a 3.07. To the best of my knowledge, GMC didn't offer a 3.23, but it is available as an aftermarket gearset.
http://www.hotjeepparts.com/products...SION-GEAR.html
Ray