Step one Think of what might happen if the bar fails while you are
driving it to see if the bar is close to right.

Step two would be to twist it back into alignment cold. The bar is
almost sure to have been heat treated ( unless you know it was made of
mild steel )

Step three would be to twist it within the limits of what you expect it
to occur in use and verify it does not take a set
( or break ).

Step four would be to do your test drive if you feel like it is safe.

Step five would be to remove it and measure the spring rate. It may
not be the same as it was originally, but it can be measured.

Note Well, I am not advocating doing this. Just how I might approach
doing it. I certainly would not try it anywhere except some place like
an airport where there is no objects that can be hit.

Dan