I was curious after I read your post here and did a little research. Lead melts at about just over 600 deg. F and boils at over 3,000 deg. F. I really don't think there would be much if any lead vapor from melting it off a car since it doesn't vaporize unless it hits it's boiling point. Sure can't hurt to be on the safe side though.If you do end up heating it out try to do it in a well ventilated area and wear a mask cause it's very toxic stuff.If bondo is applied properly it is better then lead and you won't have any issues with it reacting with the new paints.