Compare ZP PGM8.5O-3-28 USA Standard Posi for 8.5" Oldsmobile 28 Spline 12 bolt "O" Axle Now: C$32,753.39
Compare ZP PGM8.5O-3-31 USA Standard Posi for 8.5" Oldsmobile 31 Spline 12 bolt "O" Axle Now: C$38,771.49