I am not the original owner. So it's possible I have the wrong tube. I also wonder, could there be different OIL PANS with different capacities?Your part # is the correct '83-'86 dipstick.
Do you know the history of the engine?
Is it possible it has the '81-'82 tube?
Maybe if you can post a pic of your tube someone else ( I'm nowhere near mine right now) can compare to theirs to see which one you have.