On the Thirdgen 1982-1992 F-Body Camaro and Firebird you want to use a 15" x 10" x 5.5" back spacing rear rims. These rims will fit inside of the wheel well with no rolling of the lip and only minor "massaging" of the front of the lower inner fender well.
A 28.00" x 11.50" tire will fit on that rim and clear the car just fine. Any tire size larger than that will require modifications for clearance.