Each coil grounds through its bolt so that is how both are grounded. Wow that is bad grammar. Apologies.

 

I installed the new ICM and the new coils and it fired up immediately. Looks like I'm back in business.

There's probably a loose connection somewhere in my old ICM, and the act of unbolting it and bolting it back down must have allowed it to work for a while, and then the connection was once again broken when I removed the retaining bolts to install the new coils. It's a little unnerving how slim the margin for error is which can make the difference between a vehicle running and not running.