Engine/Trans angle?

[absintheisfun]

I have been trying to find an answer on this, but there isn't really a whole lot of info (that I have found) on lining up the driveline at the correct angle. I have found tons of info on Pinion Angle, but not so much on Trans/Engine angle...

Here is the best summary I have read about Pinion Angle:
Ladder-Bar Suspension 1/2 degree of pinion angle
4-link 1-2.5 degrees of pinion angle
leafs 6-7 degrees of pinion angle


So, that brings me back to the transmission. If I am fabbing my own transmount, What angle do I want the engine/Trans to aim?
The pic below is an exaggerated image to help illustrate my point. It is entirely possible that it is not important, so long as the pinion angle is set according to the specs above...but I would like to know what the suspension pros have to say about it before I go fabbing up my crossmember!


And if there is some importance to setting the angle, where do I take the measurement from?
Thanks!