tach wiring question

Got a vintage Mallory tach i,m putting in my car. Its one of the early 5 inch 10,000 rpm tach with no rev limiter or shift light. It has 5 wires coming out. Red,orange,black,green and white. Red is most likely hot and black is ground. Orange should be lighting but i,m not sure. Found a site that says the white is connected to the tach signal output of my msd and the green gets grounded. Hooked up several in my life and the green was always negative side of coil connected.Dont want to flatline the tach. Anyone positive this wire setup is correct?