5" diameter is what two of my buddies found out for their Max Wedge recreations.
On my buddy's car, we put a thick diameter of modeling clay on the underside of the hood, then installed a short stud into the carb and carefully closed the hood until it made and impression in the clay. Do this individually for each carb. Then we drilled a 1/4" pilot hole at the stud location. I machined an 1/8" thick disc 5" in diameter with a 1/4" diameter pilot hole and used it as a template to scribe a line around.