Yes, those 3 are the OD dimension available to use.
If price is not an option Get stainless with the .050″ wall thickness or similar if you are in a metric country, Thinner and might ass well get conduit, thicker it gets heavy fast. This makes the best machine, period.
Im not trying to be difficult but the more information the better. If there was an easy answer I would make a detailed explanation, but there are a world of variables. I have given dimensions and materials for the the machine I think functions in the widest variety of situations. Since you are more than doubling at least one axis it sounds like you have a very specific use in mind. 4′ wood milling 2D, 2.5D, 3D? Plywood, pine, walnut? If you have something specific it would help to know. 3D milling cabinet doors out of maple or just cutting 2D shapes out of mdf?