Thanks for your response. When I purchased the car, the previous owner had replaced the original motor with a freshly rebuilt 1988 560SL 117-968 motor, but it had no engine wiring harness. After much consideration, I decided to complete the work that he had started and go ahead with the V8. He had done SO much work on the conversion including automatic transmission fitment and exhaust installed, that I felt like it was the best path. So, I purchased a 560SL engine wiring harness and installed it. Now it's a matter of locating a few wires in the engine bay, getting rid of some duplication, and testing everything out. I have figured out most of the mystery, but this ignition wire has eluded me. I will look under the dash to see if I see the cardboard piece that you are referring to, but I fully expect that the ignition switch is wired properly. So if you have any photos that would be helpful to determine where the wire comes out of the harness, that would be great. If I need to run a new wire from the ignition switch, I'd love to know what the appropriate gauge is as well. Thanks. Julian