I want to adapt the Japanese speedometer and tach gauges found on late ‘70s and ‘80’s Sportsters to my ‘77 Superglide. Can anyone tell me where the wires go to from the tachometer? I see a lot of nos sets for sale on eBay and they seem to have 4 wires, red, white, orange, and pink. Which wires go to ignition, coil, and ground?