BROTHERS Trucks is proud to offer American Auto Wire's high-quality wiring harnesses. This harness plugs into the dash harness at the firewall on your truck. Factory Fit engine harnesses are manufactured according to the original General Motors specifications. Each part number is fully assembled, taped, and ready to install upon arrival. This harness will plug into the firewall in the factory location and will follow original routing in the engine compartment. A combination of the engine and front light harness accomplishes most functions under the hood of an early GM vehicle. Engine harness design varies significantly from year to year, but most will contain wiring for the ignition system, starter, heater blower, and temperature/oil pressure sender wires if applicable. Some vehicles used a capillary tube to provide an oil pressure reading, so these will not be included in a wiring harness. On vehicles with ignition points, the circuit feeding the ignition coil was designed with some resistance to extend the life of the ignition point set. Modern electronic ignition systems or high-energy ignition (HEI) systems do not require resistance in the circuit, so it is recommended that a harness modified for HEI be ordered if the ignition system has been upgraded. In most cases, these harnesses are available in our catalog and feature unique part numbers. NOTE: With oil pressure switch behind distributor on block.