The OEM rear rims fit the front just fine, but the wheel wells don't have room for the OEM rear tires because their diameter is too large and they rub. You can run up to a 275/35 (same diameter as the stock 245/40) up front (some brands rub, some don't) on the OEM rear rim. I even tried a 285 at one point, but it rubbed at full lock.
The OEM rear rims have more clearance for a BBK than the OEM front rims. The rim face is moved further outward, creating more clearance at the face of the caliper and more room between the radius of the caliper and the barrel of the rim.