I don’t know of any simple way to use OMC controls on a Merc. While anything is possible, it would not be simple.
If someone doesn’t have a simpler way to answer your question, I just checked and I do have enough literature to be able to give you a correct control box part number and numbers for internal parts of that control box. However, I would need to know what your serial number for the engine is and also, if you have electric start on the engine. (Not even sure that was available in ’67; but I go by serial number, not year.)
Long live American manufacturing!