OER Parts offers a wide selection of Body Panels for your 1988 GMC R3500. OER Parts offers 1988 GMC R3500 Cowl Panels, 1988 GMC R3500 Cowl Drain Flap, 1988 GMC R3500 Side Cowl Panel, 1988 GMC R3500 Cowl Panel Plugs , 1988 GMC R3500 Cowl Drain Hose, and 1988 GMC R3500 Cowl Gasket.