Well.......not exactly. Even the interior is affected. LOL You cannot get the console with shifter in the HD trucks. It's strictly a column shifter. OK...OK...your right, I'm nit picking a detail.Just about everything about the truck is different. The suspension, steering, the entire drive train, solid axles, brakes, the frame, rims/tires, towing capacity, the way it rides, way it drives. The only thing that isn't different is the interior. Its a heavy duty truck.
As Moparornocar72 indicated, the entire front clip is different. Hood, fenders, grill. I'm not 100% sure but I believe the headlights are the same as the 1500's.
Behind the front clip, I have not been able to identify an difference in the body as far as the cab and box are concerned.
The differences between the 1500's and the HD trucks so great that it is easier to list only the things that are the same, and that appears to be limited to the cab, box and for the most part, the interior.
BTW - Even the Hemi in the HD trucks is different then the Hemi in the 1500's. Part of the difference is in the MDS, but it does have a different HP/Torque rating. Some of this difference is in the PCM, some is in the engine. There are many internal parts with different P/N's.