is the OP trying to hook up a hitch? or a tow-bar?
I had to google what a BlueOx Tow Bar was, and saw this:
so I assume a Hitch and tow-bar are 2 different toys.
If OP is asking ot hook up a hitch receiver, then ARK has it spot on... and it even applies to the R50.5's (ie. 2001-2004 non-Armada Pathfinders & Qx4).
If it's a tow-bar OP is trying to hook up to the front of the Qx4, then don't you need a tow-bar "receiver" first? I assume not all cars merely come with one, and that you need to put one on...