If running stock wheels you can run 285/65R20 as a number of members have already done. Some have run without a level kit but it's very tight. A level kit will give you a bit more room. If you are running a wheel with +20 offset with 2" level it will rub and I have confirmed this with American trucks and Custom offsets although, from what I have seen, I don't believe anyone has actually tried this combination. 295/60R20 will fit with 2" level but not sure about with no level. I realize it doesn't exactly answer your question but hope it helps.Does anyone know what would be susceptible to rubbing more ? More sidewall or more width ?
Like say what was mentioned above . 295/60/20 vs 285/65/20 ( which one of these sizes for example would be prone to rubbing more?)