Raz,
You have to have the Nikasil bored out and then have it replated. I just did a CR85, depending upon what you are doing with the bike, the ports might need changed. When you bore out that large, the exhaust port and rear boost port drop quite a bit. That is good if you are looking to soften the power delivery, but if you are running MX, you might want to have someone port it before you get it replated. Eric Gorr (or any reputable builder) can give you more details.
Good luck,
Joe