I have '66 Mustang V8, high performance 289. I have Long Heddman headers, and a C4 transmission. I have tried the original starter, a new OEM starter, and a gear reduction high torque starter and none of them have worked. When I turn the car to start, the starter just "clicks". I know it's not the neutral safety switch, since it not only happened when the car was on Park, but also on Neutral. I checked the battery and it was charged. The alternator and ignition switch have all passed inspection. Any suggestions?