another silly ´68 SS Barracuda question :)

I have never spotted a battery kill switch, in any of the very few photos and articles one can find in car magazines from 1968-69.
Did the cars need to have this safety device than, or was it something NHRA ruled out for the 1970 or later season...
Question:
When was the first year, battery kill switch had to be installed, on a 1968 Super Stock Hemi A-Body?

If you have facts, pleas take a minute and clarified this.
Thank You
Stefan

I can't find a source for the year that rule came into effect, but I'm pretty sure it didn't exist in 1968.