1999 mustang wiring harness | eBay Find great deals on eBay for 1999 mustang wiring harness. Shop with confidence. Skip to main content. eBay Logo: NEW CAR STEREO CD PLAYER WIRING HARNESS WIRE ADAPTER PLUG FOR AFTERMARKET RADIO (Fits: 1999 Mustang) Brand New. $5. FAST 'N FREE. List price: Previous Price $12. 1999 Ford Mustang OE Wiring Harnesses & Stereo Adapters Ford Mustang 1999, Aftermarket Radio Wiring Harness by Metra®, with OEM Plug and Amplifier Bypass. For aftermarket stereo. Metra preassembled wiring harnesses can make your car stereo installation seamless, or at least a lot simpler..