1957 58 59 Chevy V8 283 Power Pack Cylinder Heads SBC GM Canada Factory original McKinnon cylinder heads, single camel hump from small block V8 1957 Chevrolet Bel Air 283 power pack 4 barrel, used stagger bolt pattern valve /rocker covers., casting # 1816687, No date code, sat for a very long time will need freshening up, sold as is $240.