Factory Fit® OEM Restoration Wiring Harnesses and Parts GM OEM Restoration Wiring Harnesses, Battery Cables, Switches, and Spark Plug Wire Sets. All Factory Fit® reproduction wiring harnesses are made exactly to GM OEM factory standards, using GM parts. Wiring harnesses and accessories are installed as a direct replacement to the original factory wiring – no guesswork.Classic Update Series · Download Catalog · Truck Wiring Harness - OEM Jeep Parts | JeepsAreUs A wiring harness helps in managing the electrical power that your car needs to run smoothly. These wiring harnesses relay information and electric power from all around the vehicle using an organized set of wires, terminals, and connectors. JeepsAreUs offers a selection of wiring harnesses that are compatible with various Jeep models and model years.