On both of my cars I took defunct ignition switch/coil assemblies and broke out the old coil from inside the metal shell.
I then cut the bottom of the metal shell off so I was left with a hollow tube.
The new coil drops right into the empty metal shell and the ridge around the end of the coil rests on the edge of the metal shell.
A little black silicon rubber to glue it in and seal it and its finished.

For the ignition switch part I carefully cut through the two outer layers of the armored cable (using a Dremel tool with cutting disc) to expose the ignition wire, and just spliced right into it. I used a little heat shrink tubing for extra insulation around the cut edge of the cable.

The finished result looks like factory to everyone exit another 122 owner, who might spot the second LT terminal on the coil.

Bill