wheels for the xdrive and rwd are the same. Nothing is different between the two cars in terms of wheel fitment. No idea why Carlos would say that. I believe others on this forum has already put these wheels on an xdrive car.
Also i don't believe Morr makes the front wheel in 8.5" width. The fronts are 20x9 and the rears you have a choice between 20x10 and 20x10.5. Unless they did a custom setup for you your wheels are one of those sizes.
This member has the same wheels installed on his 550xi -
http://f10.5post.com/forums/showpost...74&postcount=1
You should list your exact front and rear tire sizes. As long as you have the right tires they will work on any F10.
Alan