All trucks in the 3000-4000-6000 series use a common part number 3690029. The difference is only in the 1/2-ton which to the frame side uses brackets 3690045/46 LH/RH respectively. Even the 5000 COE uses the 3690029 on one side but uses 3703694 to the frame.
https://www.flickr.com/photos/advance-design_parts_co/14779252972/in/set-72157631868452754
https://www.flickr.com/photos/advance-design_parts_co/8129331043/in/set-72157631868452754
https://www.flickr.com/photos/advance-design_parts_co/8129510232/in/set-72157631868452754