driveshaft angles

Yes it is! With this Ford 9" I am building to go under Vixen for example. I did the same with it that I do with any other rear axle starting from scratch. When locating the perches, I get the location and width correct and then rotate the housing so the pinion ends up 5 degrees nose down and make my welds. Done many like that and they turn out spot on every time.

5 down relative the engine, or relative the ground? I think a lot of the confusion comes from exactly how the angle is measured.