These photos are of a 1500 4x4 Hybrid and a 2500HD 4x4 and are the best I could find to see differences clearly. Note the following:
1. Difference between a truck with fender flairs and one without.
2. Bumper pad on the 2500HD is 2.25" taller than the 1500.
3. Large gap between the bumper and headlights/fender on both models.
4. Hood profile on the HD is taller by about 2".
5. Fender gap of HD is double that of 1500. 1500 is 4" front 6" rear and 2500HD is 9" and 11".
6. Frame visible below body on 1500 is around 2" and 2500 is 6".
7. Lower A-arms and skid plate are visible below bumper on 2500 HD.