I have a '73 Camaro and will soon be working on the roof & quarter panels. I am not certain of the history, so how do I know if it still has the orig lead filler in it or if it has previously been filled in with something else replacing the lead filler?

 

Body shops stopped regular use of lead filler and went to stuff like Bondo, many years ago. We used to call them lead sleds, lol. But then again, when you start working on the body you will easily tell the difference between lead and bondo. Magnets do not attract either lead or bondo, but if they show no pull, then the filler is laid on pretty thick.