My guess is that you would get the Christmas Tree effect, all kinds of lights popping on.
I’ve always heard stay within 3%, but best to stay within 2.
Depends on brand of tires; how much thread is left on the front, are the 275’s gonna be 26.6” or (more/less).
It’ll be close….. but I wouldn’t exceed 1/2” difference between the 2.
Sport sizes still have negative rake like the base…only Nismo sizes have slightly taller rear tires from the factory