You certainly can machine the intake at .030 if you want to. But I've done it so many times without it and never had an issue. Now .060 is a different story. I had to mill my Ford 400 intake to match up with the .060" milled heads. It didn't lack much lining up un milled, though.
i'd use RTV on the China wall anyways... those gaskets , if rubber or cork always leak, split or end up partially inside of the intake or hang off on the outside like a death sock .
.30 milling sounds reasonable.. ill see what my guys says... we work togther for many years and if i tell him the BUDGET purpose he ll know with what i can get away :)