another f/m/j spindle question

So, after battling it out with a 5th ave, I have an M body setup. I did not however get the "knuckle arm" as my chiltons manual calls it. Did I eff up here?? Can I not use the current one? I can head back to the junkyard tomorrow if I need to. To make sure we are on the same page, I am talking about the piece that the spindle bolts to (two large bolts) and the lower ball joint attaches to.

Please let me know if I need to run back and grab these.

Thanks again!