Interesting input. Thanks!

I am almost sure they aren't galvanized leaf springs given how fast they corroded. I thought they were painted, but if so it obviously didn't work very well.

I'll dig around the inner-net for galvanized leaf springs as well as that torsion bar.

My ony question regarding that torsion bar is how to detect it is nearing the end of its service life. I, for one, am not a big fan of catastrophic failures on interstate highways?