All axle housings have a stamped two letter code on the left axle tube, usually under the brake line and just left of the brake line clip. It's shallow stamped and hard to read, and if the gears have been changed then the stamping code doesn't help identify it. A PHS report will tell you what your car was ordered with. Removing the cover and counting teeth will tell you what you have, and whether posi or open.

Available standard ratios for 1969 were 2.41, 2.78, 3.08, 3.23, 3.36, 3.55, and 3.90. Selection was limited by engine displacement and installed options. Special orders were also available.