MB GPW G503 WWII Military Jeep Wiring Harness installation MB GPW G503 WWII Military Jeep Wiring Harness installation WW2 Restoration. Installing your wiring harness can be done by one person. Instructions are fair, but you want to make sure you run the lines correctly to avoid pinching. Painless Wiring Harness Kits - Midwest Jeep Willys Jeep Painless Wiring Harness Kits Every Painless Chassis Harness comes out out of the box with the wiring already terminated to the fuse block, not by hand but with state-of-the-art packard presses. This assures you of a trouble-free performance that hand or screw connections cannot match.