How Many Grounds?

In my 65 Dart, I used the battery and alternator cables from a 90's Dodge truck that I took the mini-starter from. The neg cable had several flying ground leads, in addition to the thick block lug, so I ran ones to main frame, radiator support, and a terminal just for the headlamps. I ran dedicated returns for the headlamps, rather than rely on the sheet-metal screws the factory used.

I have found to never trust a ground thru aluminum. Once I had a Dart alternator stop working, and the problem was simply a bad ground thru the aluminum case to bracket. Another time, in my M-B, the speedometer cable started smoking when I cranked the engine. They ground the starter thru the aluminum tranny case and the strap connections had corroded, so the speedometer became the return path.