There is a good summary in some previous posts.
I have just done the mod myself, no mod needed on the front as I understand.
For the rear you can either buy the sip conversion hub or use a Dremel to take some material off the centre of the rim to alow the spacer cone to fit. You can also take 1 mm off the back ridge on the back of the rim so the face of the hub sits flush.
See here for some of the old posts.
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Anyone successfully installed MP3 Wheels/ Rims on a GTS 300?
I have dry fitted my own rims but not had a chance to get to the local dealer to get the CG2’s put on the rims to try them out due to lockdown.