Your next question will be what size thread die...I have a 3/16"x32 and 10x32
and each work...3/16"x32 is an old standard that MAY have been what was
used...some of the Tillotson AJ have a 1/4" super fine thread drain plug
screw in bottom of float well...a curious choice that I verified using a
thread gage.
Louis
Just to be on safe side take old part with you when buying a die as they
are not cheap and my memory is subject to revision when the facts come in.