2000 M900Sie is 3 bolt, but always worth looking underneath to check as both types seem to have been used at some point.
Some pictures of the parts mentioned.
Also meant to mention that I might be worth getting in touch with Nasher on here. He is gradually disposing of the estate of one of our dear late club mates. There are a large amount of silencers, so maybe there could be something of interest to you among them?