'78 was the last year that the right hand control came with a headlight on-off switch, at least in the U.S. anyway. But, that switch was somewhat "handicapped" because Yamaha also added the headlight auto-on relay that year. As soon as the motor started, the headlight was turned on regardless of what position the handlebar switch was in. Also, the tail light was no longer tied into and controlled by the headlight on-off switch. It was wired directly to the ignition switch and came on with it. If you want to add an earlier right handlebar switch with the headlight on-off switch, you'll have to make some minor wiring changes. If you want it to control the tail light too, a few more changes will be needed.