This diagram will help you change from idiot lights to gauges. I did this to my '68, which originally had idiot lights, and it worked fine. As well, for 68-69 anyway, I believe the brown tach wire was separate from the main harness. At least that's the way it was for my '69 that came with gauges and tach so that's the way I wired my '68. The job is a bit painstaking but it can be done. It helps to have the front seat and the steering column out. Randy C.