Installing torsion bars- shouldn't this be the easy part?

The load is carried primarily on the outside of the bars. But the hexes aren’t loaded like the bars, there’re basically the fixed portion with the loading happening from where they start to neck down. You wouldn’t want to gouge the crap out of them, but sanding the powder coating off the hexes isn’t going to hurt anything. As far as the heat treat goes, unless you heat them up to just short of glowing red you’re not going to hurt that.