Could a set of 3.08 gears from a 96 Impala SS be installed in a 72 Skylark rear end? They are both 8.5 rears, but the 'Lark is 28 splines and the SS is 30 splines and I don't know enough about rears to know if it is possible.
The '72 Lark should also be a 30 spline. Anyway, the ring and pinion will still swap out. The difference, if there is one, is where the axles slide into the carrier. The spline count on the axle shafts and carrier have to match. The gears themselves will bolt up to either carrier.
GM used 28 splines till 88. In 89 they went to 30 splines for the 8.5 So, you can swap gears with no problems!