You need to define upgraded modern replacement headlights

Halogen headlamps would qualify on a 71 Demon.

LED headlights for a 71 Demon show about 1.1A per bulb.
Halogen headlamps for a 71 Demon draw ~5/2.75A (high/low beam), incandescent similar.

LED bulbs generally draw a few milliamps, but that is also dependent on how bright they are. If you had a specific bulb(s) in mind post a link.

IOW, not enough info to answer your question other then to say less that original.

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They say there is always the exception that proves the rule.
Don't be the exception.