Any type wheel may be used provided it complies with the following: it is the same width and diameter as standard and as installed (including wheel spacers if applicable) it does not have an offset more than ±¼” (±6.35mm) from a standard wheel for the car.
Standard is a bit complicated, it includes factory optional wheels but not dealer options. Also, it must have been an option on your car/model/sub model. i.e. the 19x9.5 wheels from a Boss Laguna Seca edition would not be legal on a regular Mustang GT. The original "Street" rules proposal opened this up to allow diameters +/-1" from stock, but I think this went away in the latest version (?).
Tire sizes are not directly restricted, which is why stock class autocrossers are famous for stuffing wide tires on narrow stock wheels.