I have a 26x9x14 Ceros ATV Tire with the stock swingarm and haven't had any problems. One item of note or concern is you can't use the full range of a chain adjustment if you use at 26-inch tire. You can make up for this mostly with an x-ring chain, i.e. it won't need to be adjusted as much as a non o or x ring chain. I've had my Ceros on now for 2 or 3 years without any problems.
An 8" wide tire will give you more "side room" up at the front of the swingarm which curves. The side lugs on my Ceros would touch the "side front" of the swingarm before the center part of the tire does. Fred found a TerraCross tire in the size 26x8x14 and this is what I'll go with next time. Last I looked Ceros didn't come in an 8" wide 26x14.