When I got my Challey back in '75 lights dimming was not an issue, as time rolled on I started noticing more issues of this nature, I remember you could hear the heater blower change pitch with the blinkers...Anyway I went on a spree to resolve the problem...1st thing was new brushes in the alt., then went about polishing every terminal & ground contact from the alt, to the voltage regulator, battery to the body, motor ground strap to body...in the end things were back to normal with no noticeable dimming..... except when I had the stereo maxed out..
Today I'd include some dielectric grease to inhibit corrosion & improve contact.