Hello,
Well i've no idea how to load a PDF to the forum. So here's a snip of the PDF from my screen instead. Feel free to PM me with your email and ill happily send the PDF to you. The steady can be built up using 20x100mm Mild Steel flat, and 10mm Mild steel flat, 6mm and 12mm round stock. The threads can also be changed within reason to suit yourself. Its drawn in imperial as that's what bolts most old myfords use so made sense. The critical dimensions are the centre height and bore. All others can be played with easily. It can also be adapted for the 3.1/8" centre height lathes by simply reducing the centre height and then work dimensions from around the bore. The main lower body can be welded or even bolted together.

Please note the dotted line on the lower hinge part needs to be followed. I'm afraid I wasn't going to start again, If anyone notices any other issues with the drawing let me know. If there's a few ill redraw it. It dawned on me that not only would it not close if built as drawn it wouldn't even go together. Also should have written on the drawing to check clamp bolt for length from job, but you already knew that.