I am putting a 2018 Coyote engine in my 66 Mustang convertible. I bought a complete engine on a pallet with transmission, wiring harness, control module, instrument panel, fuel tank......the whole package. When it arrived all we needed was a little fuel and a battery to crank it up. Now my mechanic is confused as to where all the wires go. He's asking me to spend close to $2,000 for a wiring harness. My question is do I need a new complete harness or a new mechanic? If a new harness would be cleaner, is there a specific brand you would recommend?