Are you are currently running 9.00-20 tires on the front? If so, do your tires rub the fenders on hard turns? The 9.00-20's are the same size as 10.00-22.5 which are to big for the '56 wheel openings...which was changed in '57.
The 1956 6000 Series trucks were designed for max front tires of 8.25-20 or 9.00-22.5 (which are the same size tires).
For the rear you could step up to a 10.00-22.5 Traction...might be easier to find.
Mike B
