You can easily stretch a 245 over a 10.5" wheel. I have done it before on a standard tire change machine with little issues at all. I don't recommend it as it exceeds the recommended width by 1.5". I have done a 195 over a 9" wheel before for a VW guy. They are stretched pretty good, but no issues at all. I have never had an issue with a stretched tire rolling of the rim during hard corning, but you do run the risk of making contact with the wheel which will cause damage.
A 275 on a 10.5" wheel works just fine. 275's are rated to fit up to 11" wheels with no problems. Of course they don't look as good as a 315/35. You can also go with a 285/40 which are just about 1/4" different in over all diameter and 1.4" in tread width between a 285 and a 315.