This is true, NHRA does require a push pull type cutoff on the positive side, and also requires you to wire the alternator in such a way that it stops powering the car when the cutoff is switched. Lookup "alternator interupt"... The logic behind this is if the car crashes down the track, the first repsonder can run up to your car, pull the battery cutoff and shut the car down. The reasoning behind the positve side cutoff is that if sheet metal happened to crush the battery and is hitting the negative post, a negative cutoff would be inefective. My opinion why this doesn't matter on a street car, not fact... #1. You probably aren't wiring in the alternator interupt, just cutting a cable and putting the switch between them. So Neg or Pos doesn't make a difference. Without the alternator interupt, the car will still run if you take off the Pos or Neg cable. #2. If you get in a crash no one knows to run up to your car and flip your switch, and chances are you didn't put it in an easily accessible spot to quickly flip it after a crash, or it's the last thing on your mind after a crash.