The correct mag should be a Wico model C. It is not unusual to find others, we had an OC-3 with a Bosch, the dead give away on that one was the timing gear was moved to make it work, never could make that thing work the way I wanted. So, I put the correct Wico X on it, it did just fine. Most of these 4 cyl engines, most makes, about any flange would bolt up, they could be made to work. In those days, it reminds me of buying a battery today, if it will fit in, you can make it work.
Have a great day!!!
Andy