GMC Sierra 1500 Trailer Wiring Harness | Advance Auto Parts Advance Auto Parts has 7 different Trailer Wiring Harness for your vehicle, ready for shipping or in-store pick up. The best part is, our GMC Sierra 1500 Trailer Wiring Harness products start from as little as $14. When it comes to your GMC Sierra 1500, you 1975 GMC Suburban OE Wiring Harnesses & Stereo Adapters GMC Suburban 1975, Factory Replacement Wiring Harness by Metra®, with OEM Radio Plug. For factory stereo. This high-quality Metra wiring harness is just what you need to replace your defective or aged factory wiring harness.