Save $10 and get the CS3 in the front - unless you're tracking the car, you're not really going to notice any difference anyway. Plus IMHO, the CS3 sidewall better matches the Cobra's sidewall.
BTW - You can get that combo from TreadDepot shipped for $343.60 - saves you nearly $100. I've purchased from them before - great seller.
http://www.treaddepot.com/