1964 dart idler arm question

Well I cleaned it up and did a little bit more digging. It really didn't seem to me that this had any taper to it whatsoever. I was wrong.

I inserted a ball joint that had a similar taper to the new rock auto idler arm, And it fit perfectly.

I'm thinking that somebody put on the wrong idler arm who knows from what. And at the RockAuto arm is probably correct. I took a better picture after I cleaned it up.

Any input ?

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