I have used Millenium several times to bore and replate both Nikasil and Alusil cylinders. I specify the bore to achieve the piston to cylinder clearance I want based on the piston diameters. I have been happy with their quality and turn around times. Piston to cylinder clearance will depend on the type of Pistons and cylinders you are using.
Here is a more detailed discussion of piston to cylinder clearances:
http://forums.pelicanparts.com/911-engine-rebuilding-forum/890612-je-pistons-cast-iron-barrels.html