Then she wouldn't shut off, even with the key out of the ignition! Oops. I thought I'd created some kind of perpetual energy machine. Or, as my dad put, I'd learned how to hotwire a car (the slowest way possible).
Turns out, the old harness didn't have a clearly defined (+) line to the coil (it was lost in that awful bird's nest of wiring by the AC condensor). So when I installed the new harness, I had two hots going to the (+) side, including initially straight to the battery and not to a switched source. I've since rectified that, losing the old hot wire and keeping the new.