since I can't find the plans, I probably scanned them some time ago, here is the essence as a sketch - the radius is a "nice" match for the dial indicators, the spacing should be symmetrical, 3 or 4 inches to each side of the center - easy to make on a mill and a hand saw - bore the vertical holes to size, bore the two radiuses to make the nice curve, saw the rest with a saw, slit the ends, drill and tap the two holes, press in the dowel pin (you can use drill rod of course) and you are done.