Most parts on the B's and C's are interchangeable with a few exceptions. The final drives on the B is narrower than the C. that makes the drawbars different as well. The radiator cover is different because of the cut out for the front steering arm. The steering box on the B has a shorter cross shaft that has a smaller diameter. The front axles mount different but when starting with the radiator support down they are interchangeable.
a side note: The transmissions are the same but the B's final drive has a taller gear which makes it faster in all gears.