The 40 hubs must be machined down on the OD to fit in the bottom of the cone shape of the center of the Buick hub. The pictures of 48 hubs would show the hub hanging over the edge of the drum. Cutting the hub means the outer support on the wheel is not making contact with anyting as the drum is angling away. 40 hubs can be drilled for the small patern but must be spotfaced as the surface is angled. I am very much concerned with folks trying to use the 40 hubs and not knowing the problems. The spacing is off in every dimesion stack I have done so it is possible but difficult to get the drum to cover the shoes completly. I have seen assemblies on cars where you could look down at the drum and see the shoes.