Stop in for a cup of coffee
I never paid attention. No wonder why the relay systems make so much difference.
Yup!!
I can't swear for every year, but the ones I've had shop manuals for all show 16 gage headlight switch to dimmer and then 18 gage.
First time I had the headlight really fail was on I280 in East Orange NJ. Bad road to lose headlights; below grade and curvy. Some overhead lighting so could have been worse. That was my 75 valiant4 door with sealed beams of course. 15 amp breaker in the switch was tripping.
I've also had headlight connectors get hot enough to melt, as well a headlight switch connector in my current Barracuda partially melt. So all this got me very interested in the headlight circuits (whether I wanted to or not LOL).
The original lamps used in the mid 60s drew a bit less power than the ones installed later. If you look up the original lamp numbers you'll see the earlie rones were rated something like 50/40 Watts and later ones bump up so something like 60/50 Watts.
Maybe production engineering didn't catch that, or the lighting guys forgot to tell electric, or the accountants pushed back and asked if it was really needed....