I have what I believe to be an Olds 12 bolt differential for an A-body that I am trying to ID and possibly obtain a posi unit for. I bought it in pieces and know it is a 3.08 open rear end with 28 spline axles. Does anyone know if it is an 8.5 or 8.2 unit or something else? I could not locate any code on the axle tubes but the front of the case has part # 402227 on it. Ring gear has part # 13A40GM KZ on it. Please help. Thanks.