According to the owners manual, we are suppose to be able to jack up a 240z at the jack points along the rockers.  I did this back in the late '70s with my '73.  Then I tried again in the mid '80s on my '72.  They were both unrestored cars that lived in northern Indiana.  The sounds that were produced by thin rotten 20 gauge steel still haunt me to this day.  I am sure the titanic sounded similar as it went down. My current car is a mint condition '71.  Its frame