The stampings from overseas use a metric gage not the SAE gage that Detroit used. The stuff we get as replacement panels is lighter than the original tin.
GM built these cars out of 14 gage steel up to about 1973 when they dropped down to 18 gauge to lighten the load on the smog motors and improve crunch-ability to reduce traffic deaths in head ons.
They may have been using a lighter gage steel but either they used more of it, or they boxed things in a lot more; as in a head-on crash a 1966 is no match for a smaller 2010 car (I figured because of the heavier steel it would crush the smaller newer car, but results of testing were exactly the opposite).
Last edited by Big Dave; 07-26-2011 at 08:59 AM.