Do you have any pics of your car from the rear? I remember when a was walking back to my car and there was a newer mustang parked next to my car, it had some nice wide tires and mine don't fill the wheel wells much :(
One of the main reasons I want bigger tires is that I plan on auto crossing and doing some track days. I know I will need some big brakes to reduce brake fade, so I want to have room for upgrades. Also I'm looking for a nice big contact patch.
I have looked into wheel adapters but most of them are aluminum. Have you come across any steel ones? Ultimately I wouldn't feel comfortable using those on a car that will be driven spiritedly.