Grigg is correct, it depends. I did a study of GM Heritage Center and this is what I get. Spring steel from at least 1945 into 60-66 era. Except big trucks had Carbon steel. (About 1.5T and up).
After awhile they stopped mentioning the material.
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn
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