I came up with the same thing you did from a quick search, three different length parts or adjustable camber plates. I can't really help as to which size arm to buy.

I am not sure if the e70 is like the e46 or e90, but in those cars there is a camber alignment pin on the strut housing (under the plastic cover). You can remove this pin and adjust camber a bit. I haven't looked on my e70 to see if it also has a pin, but I am guessing it probably doesn't.

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Profeshenal spellar