Two different designs of inside door handles are seen when looking at 1939-46 Chevrolet and GMC trucks. This photo shows the attaching portion is the same. However, the opposite ends are much different.

Door Handle Mystery 1

1939-40 ' Small Ends: Were only produced by GM until about 1941!  In stock as part # DPH101. NOTE:  GM later replaced these with a the later design.

1941-46 ' Large Ends: This allows the palm of a hand to better push the handle down and open the door. (A later aftermarket company also produced this 1941-46 style). In stock as part# DPH100.