GMC - B SERIES - 1978 RSS 1978 GMC B SERIES STRUCTURE 1978 GMC B SERIES SUSPENSION:MULTIPLE AXLE 1978 GMC B SERIES SERVICE BRAKES, AIR:DRUM 1978 GMC B SERIES VISIBILITY:WINDSHIELD 1978 GMC B SERIES SERVICE BRAKES, AIR:ANTILOCK:CONTROL UNIT/MODULE