Update. I’ve owned my 54 GMC for 41 years. It was also untouched except by Father Time and Mother Nature.I’ve been sanding the interior side of the doors to prep for paint. Interestingly there is no trace of primer on the door panels but the window trim bezels had black primer like the exterior. In the years working on this truck and others one thing I have learned is don’t be surprised at what you find or don’t find.