Here is the completed tailstock base. Not much different than Gingery describes in his book. I cast it and then tried to machine it on my old CNC. That machine was not stiff enough to give me a good surface, so I ended up scraping the surfaces flat.
At first I was unsure how the large 3/8" bolt on the left side was supposed to work, but I put it in as described and it works real well at locking the tailstock down to the ways.