I don't know what there is for "our" axle but GM uses a very similar version in their trucks and the G80 GM locker works great. If it will fit our trucks, which it should, that is the way I would go.
On your '03 you may have a 10. 5 rear axle if your 3500 is a srw SO or California truck. Or did all 3500's come with the 11. 5?