Lee's post is a good contrast of how we all have different perspectives as well as different abilities and experience. It is likely there are different aspects of something I design and build that wouldn't work for Lee and vice versa. We all make our own call.
In an attempt to give you as many ideas as possible, here's mine:
Use a 10 x 33 piece of the 1.5" plate for the table and two 5 x 26 pieces of the 1.5" plate for the double beam of the base. I showed 1/2 inch plate for the ends and webs between the double beam. The base should also be closed on the top and bottom to complete the shear path for torsional rigidity. In my own design for the new base of my X3, I plan to cast a similar double beam (sans the afore mentioned top and bottom) into epoxy/granite. The E/G casting will provide the torsional rigidity and effectively dampen the structure.
The column is bolted from the bottom, through the double beam.
Joe, if you have access to a surface grinder, you could make your own dovetail ways and adjustable gibs. This could save you some $$$ but would be more work than buying linear bearings.
Cris
"Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away." Antoine de Saint-Exupery (1900 - 1944)