This is a good thread:
http://www.e90post.com/forums/showthread.php?t=508485
Bottom line, I wouldn't do it and not only because you have to replace parts. The M3 has a different braking system entirely (different master cylinder) ... who knows what kind of effect that will have on braking performance.
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2024 BMW M3 Sedan Frozen Pure Grey II/Fjord Blue, 6MT
Past: 2021 Z4 M40i Frozen Grey II/Black Alcantara | 2017 F30 340i Mineral Gray/Coral Red, 6MT | 2011 E92 335i Le Mans Blue/Black, 6MT