When the axles are made new we have a very large ram to re-true the casing and then they are machined and the Diff holes drilled.
The best solution would be to get a post 07 axle casing. They are the same as a 90 bar the Diff pcd (p38), the spring seats 10mm further outboard and of course the simple Diff pan behind the very worthwhile reinforcing ring.
If you are going to do your own then the most important bits Diff and shaft fit wise are ;
Diff face parallel to a line through the centres of each end flange.
The Diff face shoud be 42.1mm from that line.
The Diff hole rotation needs to be very tightly controlled too (can't remember without going back to the drawing).
The centre of the Diff flange needs to be on the projected line perpendicular to the face.
If you don't get that right it will eat shafts, drive flanges and probably the Diff centre too.