Those MOLDINGS are there to cover up the flanges of the roof and side-frame and the associated welds. Years ago, GM used to use a silicone bronze joint to join the two parts together thinking that the customers would object to the non-flush joint, but the Japanese proved that you didn't need to finish the joint, just cover it up. This was a real cost saver for GM and the other manufacturers, it (silicon-bronze joint) was a very costly and operator sensitive area. I used to see a lot of cars in the plants that had to be reworked over and over to get it right. Plus, the vapors and grinding dust were very hazardous materials that had to be dealt with. Just thought that you would like to know the history of the joint...
Mark