37 Chevy coupe version  

Russ Dodge years ago (and Bob Byrd and Ray Neary) taught me that the 1937 (and I think 1938) coupes have the angled line through the door that is a continuation of the front fender.  It starts pretty high on the front leading edge of the door and then angles to the bottom of the door.  Also, the side roof drip rail on a 1937 & 1938 goes over both of the side windows.

On the 1936, their is no angle line through the door, and the drip rail only goes over the front side windows, but not the back side windows.

There is also some differences in the way the rear deck comes off the roof, but the fender continuation angle and the drip rail deal are usually what I look for first when trying to find out the difference between a 1936, and a 1937/1938.