I have only done a few vinyl roofs in scale, but I have done a few chrome trim addons. My thought would be to make sections of the trim much the way GM did on the 1:1. The one long part at the edge of the trunk opening. The curved part connecting that part to the side trim that runs along the bottom of the sail panel would have to be hand bent but you're doing this with a very small thin piece of trim that can be bent and glued down as you go. I have done just this same type of bend on the top of the tail fins on the '57 Ford wagon to make a factory style tow tone. Also added some curved side molding trim added to the Suburban kit to add body side moldings. Look at using Plastruct 1.5 mm half round for the moldings. After you have the curved part glued down you can cut the end at an angle to match the lower side trim. The same thing to connect the roof drip molding down along the back side of the side window.