leif, your (67-1063) head was not introduced until '54 and is for the same bore and stroke (66 X 72.6) as your '61. It came out at the same time and mounts to the same barrel as 67-1061. I would not be surprised if both heads used the same casting, but the ST was simply machined differently. 15/16 BTW should be correct for your application, so you may, in fact, have the correct head. This would make sense to me since standard A7 heads seem to be plentiful, but I have yet to see an ST head.
Let me go dig up my standard A7 head and see what the casting number on it is.
Cheers.