I think you can put a regular 8 bolt wheel on it. (From a similar era 3/4t truck.) I've never tried though.
It may look a bit funny with 2 different style rims. Also, if you have a flat you'll need to carry one of the dual rims - just in case its a front blow out.
If you're driving through a state with retentive DOT guys, they may have a problem with it too, as your vehicle was designed to be operated with specific equipment.
You could always take off the outside tires for a longer trip, to see if there is any noticeable benefit.