things work backwards on the 66
1- the regulator should have battery voltage at one side & variable on the other side out to the alt , in those years they regulated the power side not the ground side of the field
2 - 12 v into the ballast & approx 8 at the coil feed side
3 - Variable , same reading as the wire out of the regulator .
4 - 13v not running , 14.2 approx running
5 - coil should be battery v when cranking & drop to 8-9v Key on or running