I contacted Oregon's technical support department which was quite helpful. They took a day or so to do some research, then got back to me with a G6 part number. 396-727 which was the one I'd figured would fit based on dimensions.
Also talked to my local Husqvarana dealer who really only wanted to sell me an Husqvarna blade even though they are also an Oregon dealer. He mentioned there's a heavy duty blade from Husqvarna that's 3" wide.