gwater15. The difference between the '39 and '40 is as follows;
The '39 has a narrow upper bar and 16 lower cross bars.
The '40 has a wider upper bar and 15 lower bars. I believe these are the correct numbers but at least the '40 has one less bar than the '39. The lower bars are the same ones on both years. Also the '40 has parking lights on the top of the front fenders and has the '41 to '46 instrument panel.Hope this helps. ps. I have a 1939 Chev Suburban myself.
Stan Norrish