Pinion angle?

Going to be putting my rearend this week and looking for a little advice on the pinion angle. I am getting some conflicting advice. The tailshaft of my transmission is currently at 0* The car will be used 50 street 50 strip. Some have told me to set the pinion angle to 0* so the transmission and pinion are equal, others have told me to set the pinion angle 7* down because of the rearends twist. any help is appreciated.

Greg