OER Parts offers a wide selection of Brake Components for your 1978 GMC Truck. OER Parts offers 1978 GMC Truck Wheel Cylinders, 1978 GMC Truck Front Wheel Cylinders 1978 GMC Truck Rear Wheel Cylinders, 1978 GMC Truck Wheel Cylinder Retainer, 1978 GMC Truck Drum Brake Bleeder Screws, 1978 GMC Truck Front Wheel Cylinder Repair Set, 1978 GMC Truck Rear Wheel Cylinder Repair Set, and 1978 GMC Truck Wheel Cylinder Pins.