[Redog]

I don't know if they used these in 1971 but you could look for the RPO codes on the trunk lid

It would be a "GU" code like GU2 GU3 GU4

Assuming nobody changed the rear end

Here are some:

GU1 : AXLE REAR, 2.41 RATIO

GU2 : AXLE REAR, 2.73 RATIO

GU4 : AXLE REAR, 3.08 RATIO

GU5 : AXLE REAR, 3.23 RATIO

GU6 : AXLE REAR, 3.42 RATIO

GV1 : AXLE REAR, 2.73 RATIO

GV2 : AXLE REAR, 5.83 RATIO

GV3 : AXLE REAR, 3.08 RATIO

GV4 : AXLE REAR, 3.36 RATIO

GV5 : AXLE REAR, 3.55 RATIO

GV7 : AXLE REAR, 4.11 RATIO

GV8 : AXLE REAR, 2.72 RATIO

GW2 : AXLE REAR, 2.56 RATIO

GW3 : AXLE REAR, 2.56 RATIO

GW4 : AXLE REAR, 3.31 RATIO

GW5 : AXLE REAR, 2.73 RATIO

GW6 : AXLE REAR, 3.27 RATIO

GW8 : AXLE REAR, 4.10 RATIO

GW9 : AXLE REAR, 2.93 RATIO (DUP WITH GU3)