For 1979-1996 GMC P3500 Disc Brake Rotor Rear Centric 1980 1981 1982 1983 1984. 1979 GMC P3500 Position: Rear;. 1980 GMC P3500 Position: Rear;. 1981 GMC P3500 Position: Rear;. 1982 GMC P3500 Position: Rear;.