Wiring up a tach?

Not unless you turn the key on and leave it for an extended period, and maybe even THEN it won't. Don't you think the possiblility of a fried coil is a lot better than an empty parking spot?

All the switch does, is the very same thing that the points or Mopar ECU does, IE switches the neg. lead of the coil to ground. If you turned the key on with the points closed, same thing. If you turn the key on with a Mopar ECU, same thing.

Only ignitions that do NOT put current through the coil with key on/ engine off are such things as CD (MSD) and GM HEI modules.

If someone tried to hotwire the car by jumpering a 12v hot lead right to the coil + It MIGHT fry the coil, but in that case they sure as heck are not gonna drive off with it!!!