Some of this advice runs contrary to what I have always done, and what is generally recommended for street rods.

Nitro,
If you load this thing it's going to make the 4 bar set change instant centers as the bars torque and pull
Since in most triangulated 4-bar suspensions, the upper and lower bars are parallel, I can't see any reason for a change in instant center. Am I wrong here?
Be on the safe side and get the tranny to point directly at the pinion.
I've always heard that this is a good idea on a race car, but undesirable on a street car.

Are you guys recommending that both the trans and the pinion point down? Conventional wisdom has the pinion pointing up and the trans pointing down in equal angles. That makes the centerline of the pinion and the centerline of the trans output shaft parallel.

http://www.iedls.com/ptsetup.html