The rear Cobra brakes will fit with most 15” wheels.  The GT or v6 front brakes will not work on your car. The reason is the original five lug front hubs will not fit inside the smaller rotors of the v6 or GT brakes. In order to make them fit inside the smaller rotors, the OD must be machined smaller and it reduces the margin around the wheel studs, making it too thin. During the design process, I decided the margin was insufficient to properly hold the pressed-in studs without the cast iron hub possibly cracking, creating an unsafe condition.
The late model cars use a steel hub and the splines on the wheel studs are significantly smaller, making for a larger margin around the studs.
Yes, you COULD make the smaller rotors fit, but it will result in a possibly unsafe condition, which is what you are trying to avoid by installing disc brakes in the first place.