The general rule of thumb is that the tire should not be more than 4" wider than the rim, which would mean an 11" tire on a 7" rim. But many people have rum 11.5s on 7" rims. It's safe enough.
Clearance is an issue, however, if they are factory rims. Take a look at how close the rear tires are to the leaf springs, then extrapolate to how close an 11.5" tire will be. Then allow for the extra bulging of the sidewall if you air down.
In the front, 10.50s rub significantly on the lower control arms when turning. 11.50s will extend inward an additional 1/2", so the problem will be even worse -- meaning you'll lose even more turning radius.
It's safe, but not an ideal setup.