Here’s an old version of the main body of my rear axle end housing with booleans (but only those for the bolt holes):
https://www.dropbox.com/s/bhpk4e9cvewafno/RearAxleEndHousing_OldBooleanVersion_4Juli2020.blend?dl=0
I’ve also cut out and magnified a drawing of this part from an earlier post in this thread which seems to show some kind of contour lines that can maybe give a hint on how to do a proper topology in order to match the exact shape:
