The base/clear guy might be the best way to go. It is not original paint on the quarter panel anyway. I don’t know when acrylic enamel became available to shops but I first saw it in the early 70’s. My guess it has lacquer on the repaired panel. From the view in the second pic it seems like they didn’t get a good match back then. It is true that acrylic enamel can be blended, they even used to make a “color blender” which just worked like the base/clear the first shop suggested. That car looks awesome and I think a good painter could duplicate the original finish very well.