[Zoomad75]

The vin will tell you the exact year. 89-91 used the same grill for the Silverado models like in the pic.

90-91's will have some unique items like an electric speedometer with 6 digit odometer. The 90-91's also have roof mounted 3 point seat belts for the rear seat passengers.

The auto trans 700r4 was renamed internally as the 4L60 (no "e") by 90. The "e" is what stands for the electronic control function which the 700r4/4L60 did not have.