If the only concern is the camber it might be better to cut the original rear arm and weld/sandwich a piece in to lengthen it, doesn't make the adjustment friendlier though. I "think" the stock front arm should work as is but I might be wrong.

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)