Below is a copy of the 37 passenger car accessory book for your enlightenment.  This will make it easier to identify original GM accessories from after market.  I really love the prices.

Please note the "wheel disc" (full hubcap) below is a 1937 only accessory.  If you have a chrome disc that fits under the small hubcap, it's a 1938 only.  Note also that the 37 hubcap has red Chevrolet and blue speed streams.   The 38 hubcap has the colors reversed.  The Australian Holden has Chevrolet in black and no speed streams.  Click on hubcap above  to view the hubcaps in Paint section.

 

    If you read closely, you'll notice that the center radio (above) is designed to fit other vehicles.  If you click on above page you will see it listed in truck accessories.  Look at the accessory to the radio's left in Truck Accessories!!!
    Sometimes you will find a heater that looks like the one above but says Harrison instead of Chevrolet.  Nothing like some badge engineering.  Look closely at the defroster at the bottom of the page above.  It has one spout above the gauges with a trapezoid diamond stamped in it.  If you have defroster holes in the window moldings on both sides, you have a 1938.
 
 

    The brake lever extension below tempts drivers to hammer down on it to release the Emergency Brake.  This results in Pawl damage.  You should pull the brake a little tighter, squeeze the handle and release the brake.