Somehow I managed to create 2 threads.

It was the alternator. The reason I didn't swap it out right off the bat is because the charging system schematic had me confused and I couldn't understand why the idiot lights wouldn't come on with a dead alternator. After tracing all the wires from both sides of the battery light and some help from this site I finally realized that with the car off and ignition switch on the battery supplies 12V to one side of the bulb and the other side grounds through the alternator. So if the alternator fails in a way that disrupts the ground path the battery light won't come on. I'm no electrical engineer, but that strikes me as a pretty silly design that lets the alternator fail without giving the driver any indication. I guess it was pretty common in that era though, although I don't remember it being the case on American cars.