If you've got an iPhone, download the free 'Tremec Toolbox' app.
It works great. You measure the angles with it and it tells you if they are acceptable.
All you need to know.....
Nose of axle should always have a slight downward angle, to counter the reaction to drive when moving off, which will force the nose upwards again.
Installing an axle already pointing upwards would be a very strange thing to do unless whatever axle mounting design you're using is equally strange.
its a gm 10 bolt axle
its mounted on the std leaf springs with no shims