The new ring & pinion sets fit '64-'72 differentials, IIRC.
The 4.11 gears are often found behind automatics, but they can also be found in standard shift trucks.
It's easy to tell the difference between the axles used in '67-'72 3/4-ton trucks - only the HO-x2 has a drop-out differential in a banjo axle. The others are of a more convential design.
