The fog light mod is really common. You bug the foglight power into the convertible top harness that every mustang has regardless of whether it was a vert or not. This allows you to run your fogs independently of the headlights regardless.
Although fogs being on at the same time as the high beams is 100% completely pointless and is only for looks.
2000 Mustang GT Steeda #0048
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.