Canadian cars used to come with Cobra stickers on the back as a sales tactic..no diference from the GT at all. The only fox Cobra was the 93+years. First before you speak about adding serious power you need to know what kind of "roller cams" you have cause you only have one and the 88 HO's came stock with a roller cam, also curious why you would need custom headers because you didn't mention any odd heads so I am confused.Didn't mention wether your car has been converted to mass air or not possible you should look into that before you continue to mod. To be very honest it sounds to me like you have been fed a few lines by the previous owner to make the car sound more attractive to you. Not trying to be an A** just my .02 $