As it was already mentioned, the originality of where they came from may have some purists shrug a bit when seen on a Mustang, but many younger owners may not know, or care.
I always related them to Chevy using them on the Grand Sport Corvette years ago as a tribute to Zora Arkus Duntov, and his GS Corvettes. The other write up was interesting too (using one, two, and three stripes for the pit crews to track multiple team cars).
Then I saw where Dodge used them first on the Viper, then on other models. At that point, it seemed the "GS" meaning flew away, and now they seem to be better known as a Dodge thing.
Not a fan of them, but have no worries if folks put them on their vehicle.
Just not on a mini van please.
It is better to keep your mouth closed and let people think you are a fool than to open it and remove all doubt.