Hi all,
Adding to the thread as I just successfully completed this job. For my manual 340i-Xdrive, it needed PN: 33108659988. As mentioned above, it did require purchasing the non-xdrive rear axels (33207597685) and (33207597686) as well.
Here are some pics of the diff mounting point when grinding it down 10mm:
View post on imgur.com
I ended up buying some generic
M12x10mm Spacers which worked quite well. Overall fitment is great, really glad to have the stronger axels too. Will see how it holds up over time.
I plan to drive it 1000 miles before swapping the fluid to
Motul Gear Competition 75W140