Rita Hayworth did her part... so if you come across her big old car with no bumpers, now you'll know what happened to them.
http://www.sptimes.com/2005/08/28/Worldwarii/War_changes_fashion.shtml
For an example of immense largese in donating to the scrap drives, read about Panmsy Yount's 1933 Duesenberg Model J Judkins Berline that was turned over to the war effort for it's use as metal for armor plate, or whatever they did with all that steel http://justacarguy.blogspot.com/2008/08/ive-posted-before-about-ww2-scrap.html