You would have a much easier time of "shutting off" the coil if you placed your permanent kill switch in the 12V lead that supplies power to the coil, rather than the high voltage lead to the distributor. Most of the reason that the high-tension lead to the distributor is the one that usually gets pulled is that it is easy to do, for a temporary fix. If you want to go permanent, stay away from the high-tension lead! The problems with switching off the coil may be more trouble than they are worth, though, because of some of the other devices that receive their power from the coil. Look at the bundle of wires attached to the "+" side of your coil sometime! It can still work, if you put the group connection away from the coil, and run a single lead to the switch, then to the coil.  Slightly more complicated, but easily doable. Again, it comes down to how much trouble you want to go to.

Evan Mac Donald

1984 Wolfburg
1985 GL 7 Pass.
1991 Carat Weekender