I disagree. I have 275 40's on the stock Cobra Rim and they do not have the squeezed look. I've been running these since about 1997. However, I am about to upgrade to the Torque IIs 17x9.5s. Can't wait. You will be fine though. Peace
Go onto whoevers tire it is you want to buy website, they have recommended rim width for tires. squeezing a 275 on an 8 inch rim and putting a 245 on an 8 inch rim actually won't get you much more tread width. 9 inch rims with 275s are about as much as I'd go, but that's just me.