Note: The schematic for 1975 models does not show the second light-green/white wire from the coil +ve to the solenoid, but they do for 76 and later. It's not known whether this is an error in the schematic or an omission in the harness and solenoid, I can't think of any reason why it should be intended to be like that.

Information on the ballast resistance can be found here.