My Yellow Stang

First which drive shaft, I want a striaght bolt in but I have found 4" tapering to 3 1/2", 4", and 3 1/2" which is preferred. From I have read the pinon angle will have to be changed so which way do I go, Adj. upper control arm, Adj. lower control arm, or both. Does anyone know the angle should be with the Al. Shaft. The reason for the questions is I am changing my rear gears, 3:31 to 3:73, and want to do everything at the same time. So far my mods are, Off Road H Pipe, JLT Cold Air, Brenspeed Tune. All I can say is WOW. So Now I Need more.