to clear the calipers you will need later model mustang wheels, ones that came on the 94-04 mustangs should fit nicely.
another option would be to use wheel adapters. normally this is done when changing the wheel bolt pattern, but there are ones that maintain the bolt pattern, but move the wheel out about an inch, and that will clear the caliper. and since the adapters bolt to the hub, there is no issue that comes when wheel spacers are used. you dont need longer wheel studs, for instance. but you will need a some red loctite to make sure the inner lug nuts dont come loose.