It was an issue when the cars were new. The cam tail on the cars created a low pressure area and exhaust gasses were sucked up around the bumper and the aluminum trim piece along the trunk (on the GTs) as well as on the trunk lid. On a long trip my '65 Dart GT bumper would be blue above the exhaust extension from the heat and exhaust fumes. Remember we were using leaded gas back then and the exhaust fumes were more noxious then than today. Most HiPo 273 Darts have much more corrosion on the left side of the aluminum trim piece than the other side due to that very issue.
