School the rookie on 8.25 rears

It depends on the gear ratio in the 80's cop car rear and the ratio in the A body rear, if they are both 2.76 or numerically higher then yes you can plug and play, also if both gears are 2.41 or numerically lower you can mix and match. The 2.76 and higher carrier isn't compatible with the numerically lower gear set, also the carrier bearing size changed in '75 so depending on what year the A body rear is you might have to change bearings on the carrier.