Off set rims
 

I want to put 31's on my truck but the previous owner had a major problem with them rubbing on the frame and sway bars. What rims would y'all recommend?

Stock Ranger wheels usually have 4.5" backspacing. This means the tire will be inside the fender well more and have a greater chance of rubbing on things such as the sway bar. You can try wheels that have a 3.75 backspacing, and that may keep the tires from rubbing as much. However since your truck is 2wd, you may need to lift it for the 31's to clear regardless of wheel backspacing.