Although that is ia Truck transmission (looks like a '56), theres not any difference in the car and truck Ford-O's besides the converter housing. I am pretty sure that is a pressure test port. There is supposed to be a pipe plug in there.
You say that 3/16 tubing is coming out of that fitting? Its hard to see because the passing gear link is blocking the view.
There is no good reason to do a pressure test from above, since the adjustment is made from below. ???