The original coil with armored cable had been replaced at some point with a Bosch blue coil. The previous owner left the old coil (not connected) in place simply to plug the hole in the firewall. I found this an inelegant solution, so I crafted a blanking plate from some aluminum and chucked the old coil.
Cage nuts are used to secure the coil to the firewall. I'm missing one, and I've had a terribly difficult time locating a spare. I finally realized that they're used in rackmount equipment; unfortunately, they're typically sold in bags of 100, so now I have to find a way to get just two. In the meanwhile, I'm using some 3/8" nylon body nuts.
Coil wire was rerouted (for now, through the temp sender grommet).