A few days ago in another discussion (related to a set of unrestored pictures I posted) Ed mentioned the following after I posted the following picture
The 2 holes that were drilled at aosmith for the 2 round rear tag lights have reddish primer put over the new raw metal cut holes to protect the metal inside holes from corrosion and help seal the hole when the c4tz lights were pushed in place and the excess primer always runs down inside taillight panel as I have seen this many times on unmolested 69 shelbys. ..............
In that thread I mentioned I would start a new stand alone thread on the subject so pictures could be posted and to make it easier for others to find and apply the details as they choose.
I had not recalled seeing the detail but going back through pictures I had and had documented it. In fact I believe that is Ed in the background