There are no issues with running a 9" wide wheel for those tires. The taller the tire is the less effect a narrow rim has on it......same concept as how you can have a 12" lift on a longbed pickup and the rear driveshaft angles are okay, but are a nightmare on a short K5. A 33x15 probably wouldn't work that well, but a 42x15 is not a problem. Also, I wouldn't be concerned about the rims causing wear or handling issues considering you are talking 42" bias ply Swampers. A friend of mine has ran 42's on 8" wide rims for years and used to drive his truck to the trail all of the time on the freeway on multiple hour long trips. I've ran 39.5x15's on 8" rims also for years. I do haul it on the trailer, but almost all of our off-road trips require some driving on asphalt. The street driving isn't great but have always contributed that to low tire pressures, welded rear diff, no swaybar, etc...