This is a pic of the finished intake manifold. Sorry, not a great shot. Compare to the stock pic.
Manifold spacer (in front) has been matched to the I.D. of the manifold, all ridges and casting marks have been removed, and the mounting rubber interior has been matched to the manifold I.D. also. After this, the entire interior was roughed up with an 18 tooth/inch hacksaw blade, and 40 grit snadpaper to roughen up the surface and prevent any air barrier layer from forming.

The shiney stuff makes for a better pic though!