GM Original Equipment™ Engine Coolant Radiator (20678) by ACDelco®. Core Size: 26 1/4″ x 15″ x 1 3/8″. The radiator is the heart of a vehicle’s cooling system. So, when it comes to replacing a worn radiator, you need a product that will match the original factory part in fit, form and function. ACDelco offers dependable, long-lasting GM Original Equipment™ radiators for GM vehicles. ACDelco radiators are reliable, corrosion-resistant, and lightweight to provide optimal heat-transfer characteristics. Don’t trust your customers’ vehicles to anything less than ACDelco quality.