265 on a 10.5 isn't that much of a stretch. You'll be fine, it's not enough stretch to worry about blowing a tire off or the sidewall failing. Maybe just be a bit more careful around curbs and potholes. On my old car, I had a 255 on a 10.5 and that wasn't even much of a stretch. But I have to ask, why are you stretching? If your wheels are that aggressive and you've already modified your fenders, then fine, but if you haven't done that yet, there is no point in stretching. If your car isn't slammed and your wheels aren't too aggressive, stretching the tire looks really silly.