Rob,
Have you stripped the paint off the firewall yet? Pay particularly close attention the the recessed area of the firewall behind the distributor, the area above and to the passenger side of the wiring gutter and the top of the drivers side cowl area where the hood stop is mounted. Almost every leads car I have torn down or seen close up had similar markings in that area. Just curious what yours may have. Thanks for sharing your photos. I can expect copies in the mail............?
Rick