A 265 tires is approximately 10.5 inches wide. The general rule of thumb is that you can run tires up to about 4" wider than the rim width without any problems, so running these tires on 8" wide rims is no issue at all.
And before anyone starts saying how it is possible to run tires more than 4" wider than rim width, yes, I know. If you are going to do that, however, you should understand all the issues related to tread width, sidwall bulge, inflation pressure, and so on. Anyone who understands all these issues won't need to ask questions about how wide of a tire they can run.