I looked at the 1970 accessories brochure. Page 21 shows an instrument panel warning light option that includes a 'headlight on' warning light.
http://oldcarbrochures.org/United%20...sories-21.html
There's also a taillight monitoring system option as well as the headlight delay option on page 24 (the taillight monitoring system uses fiber optic cables so it wouldn't be that anyway.)
http://oldcarbrochures.org/United%20...sories-24.html