ahh- As I see it, (on the 123 cars that I know) 2 types of axle shafts are used- homokenitic(both ends the same) and annular. (different ends). while different, they are interchangeable.
the annular units have a removeable end on them like you are referring.

while this does not help you find your part, it may help other peeps understand what you're after. also you may be better off finding a complete axle.

of course, I could be wrong.

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1984 123.193 372,xxx miles, room for Seven.

1999 Dodge Durango Cummins 4BTAA 47RE 5k lb 4x4 getting 25+mpgs, room for Seven.