unless the coil is giving you a dead short you don't need to remove it or mess with the armoured cable. On all of my 120s I have just disconnected the wire that goes to the dizzy clamped a new coil to the old coil body and wired appropriately. The wiring is simple, but you need to take into account you will get no current to the new coil using the old ign., switch. Personally I have always replaced the old switch with an appropriate universal switch. Tuck the old one under the dash ...perhaps in the future some lucky person will resurrect it. Speaking of which....poor contacts/short in dizzy etc are the usual causes of "coil failure" All the coils I bypassed were still good after 30-40 years in service....I just like modding to electronic /transistorized ign as it really helps the engine and life is too short to spend it adjusting points/dwell/changing condensors.
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Patrick ('68 220, '83 245).