275's are fine on an 8 inch wheel in the back. For standard radials, just know that you will sacrafice some life of the tires, and they will not perform as well since you are squeezing a bigger tire on to a smaller wheel(unless the brand runs narrow, like nitto drs). I've run tens of thousands of miles with 275/40's out back on 8 inch wheels in mustangs, with many different brands. They definetly look cool. I've got a sweet go pro video of a 600rwhp Vette dynoed today, with my go pro camera facing down on top of the tire from 70-140mph on the dyno. The tire litterly goes out of site on CCW wheels at the top of the pull.
I have realized that tires are on the car for one reason. And that is to perform. For me, it is the lightest wheel/tire combo with the best grip in a strait line for the street, and switching out an extra set of stock rims for 600+mile road trips or if the weather forcast is bad, or it I get called out to a local road course. I still run the same size you are talking about on the street, 275/40-17, but in a drag radial and will be approaching 900-950hp at the crank very soon. Where you live, you and your friend have little to worry about for all season tires.
Also note that the 255/40 will have a smaller sidewall than a 245/45. While you gain width, the sidewall is almost 3/4 of an inch smaller. A good front tire option, but a very poor rear tire option.