Without a starter heat shield, I sometimes have about 10-15 minutes that nobody could start mine until it cools down anyway.

I favor the "keep in site" method anyway because a club or ignition disabling won't stop the tow hook or strip-in-place-in- seconds. My other favored method is to simply avoid the higher theft/vandal areas. I cannot even recall the last time my '68 has crossed into the Chicago city limits. (Maybe 35 years?)