The "bottom" of the stem should also have a cylindrical projection down and below the "bracket" with a wide "slot" in it... If this and the 6mm threaded hole are in the casting, It is quite easy to just "bolt-on" the components......IF you can locate them all....
I am attempting to "stockpile" as many of these components as I can, and hopefully piece together "sets" for the various bikes that used them, and make them available to those who want them........ ALL donations gratefully accepted, even "broken" parts and partials...... Steve