Well once you ditch the 10.25" in the back and hunt down a Dana with a tube long enough to handle the wheel backspacking without rubbing on the springs and get it put in, then yes, you can run spacers between the wheels so the tires don't rub on each other.

If you could find a D110 geared the same as your front that'd be a start in the right direction. Your 42s look kinda stuffed in the rear, so what plans do you have for clearing one 46 on a side before you try to shoehorn a second one on there? Trimming the fender behind the dually flare would probably open a lot of room, but maybe not enough for the outer tire to clear the new flare.