How do you tighten the LCA shaft?

Get out your pair of vice grips, and clamp it down onto the shaft, up in the space where you can get to it in the crossmember , where it goes in.
That's what i do at the wrecking yards when removing a LCA, when the bushings are totally shot, and the nut and shaft spin together.
Easy peasy.

Ok.
Edit.
Here's a picture for you.
You can figure it all out from here, what i'm talking about.