There's nothing "wrong" with running different brand tires like that nor does it pose a safety threat. I personally would be driven crazy looking at different sidewall lettering & tread patterns when looking at my car. My only question to you is- how wide are the rear rims that you're mounting those 315's on? Ideally you should be mounting those 315's on at least a 10.5" wide rim for safety reasons. I know that many guys have mounted a 315 on a 17 x 9 factory rim but you're going to have a lot of sidewall bulge which will harm your contact patch to the road effectively negating the purpose of a wide tire.