Hi guys,
After much searching, I wasn't able to find a clear answer on which Bosch part numbers matched up with the N62 4.8is engine for the O2 sensors. Well, here is the answer that I put together:
15682 Downstream Right - 11787506539 449MM
15335 Downstream Left - 11787524530 1150MM
17255 Upstream Left - 11787530736 840MM
17254 Upstream Right - 11787530735 480MM
You can use this to double check:
Bosch Vehicle Part Finder
And RealOEM.com too:
RealOEM.com * BMW E53 X5 4.8is CATALYST/LAMBDA PROBE
I cross referenced the length of the cables.