[DanEC]

Kevin - If you don't think it coming through up in the top, outside of the cowl there is another path. At the rocker panel there is a small gap between the outer rectangular frame member and the round tube that the body is riveted to. Even with the foam closures in place in the vicinity of the firewall, heat from the exhaust can rise up through that gap behind the closure like a chimey and out around the hinges. That's why sealing it up good around the hinge/door jamb area is a good idea.