Stand alone coil $20. Armoured cable coil $730. You're destroying the later to basically change it to the former.

If you want to be destructive, do it neatly and carefully drill a hole in the centre of the cap on the end of the coil. Use a spot weld cutter so you only just break through the metal. Solder a length of thin red wire to the existing solder connection, which is the + wire from the ignition switch. Use a blanking grommet with a very small hole in to seal the coil back up again. Thread the new wire through the bulkhead and attach to the Petronix red wire. This will be hardly noticeable under the hood if done with care.

Using the diode kit is cheap. If you already have the late type starter it's even cheaper and with both methods you still have your $730 coil.

Idea. Swap your intact functioning coil with someone who has a wrecked one and charge them the price of the Pertronix.