Morris Minor Owners Club

I think that you must be misreading the PDF as ALL 'A' Series axle diffs are interchangeable as complete assys. The main differences are and which have to be taken into account when interchanging diff assys and or parts is the position of the oil filler plug and the diff carrier which can be a ATA carrier or BTA carrier. The BTA carrier is stronger and should be used in all performance applications. The PDF goes into some detail regarding interchange ability of carriers and crown wheel & pinion (CWP) sets.
Phil