Let's talk pinion angle

Getting ready to put the rear end back in my Dart after some maintenance work. This is mostly a street car / occasional drag car. What pinion angle am I looking for? Seems like 2 to 3 degrees down is what I remember. So would that be down from drive shaft angle or from level? Does adjusting the pinion have an effect on launch 60' times or is it just for u joint survival?

Little side note I'm running 3"de arched SS springs and no pinion snubber.