AF is the 3.90 gear, 3 02 is the date code, March 2nd. 9 3/8 is the ring gear diameter. Not much available aftermarket as far as gears/Posis/lockers go, there is a 3.38 replacement gear and I do know of a 30 spline upgrade axle shaft kit, but that's about it. Seals, bearings, and gaskets are redily available.
The 3.90 gear works very well with an overdrive transmission.
