[dsraven]

like said. the confusing part is yet to come. leaf spring wind up factor. some guys fudge the pinion angle because they have big motors and when they "hit it" the spring wind up from acceleration changes the pinion angle a bunch and causes vibration under load due to the working angles of the u joints being so different. ask any 4x4 guy who has a spring spacer block lift kit and he will tell you all about his troubles. one reason why some guys go with a 4 link rear suspension or have fancy looking traction bars.
just set the pinion angle to be opposite the trans angle and go with it.