I've attached a sketch showing the location of the 0.250 dia steel pin and the attach screw that has a head diameter of 0.500 inches. I tried to measure from known features to make it easier to interpret (see the photo for detail). Notice that when the hook is pushed back and away from the spindle it sits on the pin, with the bottom of it parallel to the bottom of the headstock.
The thickness of the shim between the headstock casting and the hook is 0.300 inches. The casting surface does not appear to be faced around the pin or the screw, but I was not able to remove the screw to perform a detailed inspection. I was going to do a nice SolidWorks sketch for you except I am having issues with my latest license not installing properly.
Let me know if you need additional measurements or if you need help interpreting my sketch.