I am in the process of installing a new centerboard for my 1986 O'Day Daysailer III. I bought the CB from Rudy at DS Marine. He has a template, provided to him from O'Day, that lays on top of the CB and shows the position of the holes for the CB pin and the downhaul line knot. Here are photos of the new CB, in it's crate, as shipped to me. Rudy drew the circle for the pin that the the CB will rotate on and the spot for the hole for the line. Also on top are the points for the three holes required to bolt down the stainless steel uphaul line bracket. I marked up the CB (actually drew on tape, not the CB!) to show distances and locations of the holes RELATIVE TO THE RECTANGULAR OUTSIDE DIMENSIONS, not the curved edges. Use this information at your own peril. Measure twice, cut once. I take no responsibility. OK, now that I said that here are the images. I will post photos of my CB after I rig it and before I install it.
Steve