Just random ebay browsing and saw this ...

http://cgi.ebay.co.uk/BMW-E39-5-SERIES-DIFF-MANUAL-2-93-RATIO-528I-530I-535I-/250515142823?cmd=ViewItem&pt=UK_CarsParts_Vehicles_CarParts_SM&h ash=item3a53ddb8a7

Thought it may interest the BEC boys. A list of diff ratios fitted to some model (i've no idea what an E38 is).
http://www.bokchoys.com/differential/GearRatios.htm

No

Its a late 90's to early 00's 5 series - probably too heavy???

I have a 2.28:1 from a 330 diesel, that I'll eventually get around to fitting

Similar price but from germany.

ATB

Simon