I am looking at purchasing a 2005 3500 6 speed 4wd drw quad cab with a flat bed. It will replace the 2500 on my signature. The truck in question has a 4.73 rear end. The tires will need replacing before winter. It currently has 245's on it. The sticker calls for 235's. I am running 285's on my 2500, but it only has single rear wheels. Here are the questions:

1. Is there any advantage to going to a tire bigger than 245?

2. How large can they be before the duals will start interfering with each other under load?

As far as I can tell this machine is completely stock. It has about 144,000 miles on it.