Need thread spec for "MS PORT PER SAE J 1926-1-4"

Would someone be so kind as to look this up for me, or suggest where I might look on the internet for the spec?
I'm drawing up some tooling, and I have to come up with a spud to go
down the throat of a "MS PORT PER SAE J 1926-1-4" which is nothing but a boss with an internal thread, cut from 7/8 round stock. I'd really, really like to know the minor diameter of that internal thread, if anyone has the reference handy, or a link.
Thanks a Gazillion! Rich
I sincerely apologize if this got multiple-posted; that google interface is a nightmare; but I'm stuck with windows while using AutoCad, and have removed the M$ "newsreader", Outlook Express. (Or, Butthole Distress, depending on your POV. ;-)
Thanks, Rich
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