Originally Posted by HP Autowerks
The front is fairly easy, a pair of sleeves would adapt the non-M struts for M use.
The rear need to be pin to eye instead of pin to pin. The rear E9x dampers are dimensionally similar to an E36/46 M and naturally most if not all the damper manufactures just go back to their parts bin for it.
Harold, this was exactly their concern as they do not prefer the sleeve idea on the front shock body and would rather design a larger diameter body to accommodate the M3.