According to my Guy Fay tractor data book, K stood for cast iron pistons. A or B was for distillate or kerosene respectively. in addition to the hole you mentioned, look for a petcock to drain the carb, a heat shield, or remains of it, over the manifold, and /or a squared, boxy looking manifold.
"The Constitution is not an instrument for the government
to restrain the people, it is an instrument for the people to restrain the
government lest it come to dominate our lives and interests." Patrick Henry