Personally myself, I would get a chuck back plate of a larger size, like 8", drill and tap holes as you need it for holding your parts. You don't need slots in it as they thought you needed back in the old days. I have one set up for my 13" Sheldon lathe that has a L-00 register on it. The only thing I've really done with it, was mount a small angle plate to it, to hold some brass cross feed nuts on it, to drill , bore and thread. Worked out to be a nice fixture.