What is the procedure for changing the axle weight rating of a truck. For example if the axle and springs from a 3500 truck were installed in a 2500, would adding a label on the door jam indicating the change and the new axle weight rating be sufficient or is there paperwork that must be submitted to the licencing office?

I am not sure if you can increase the weight rating of a truck after it is manufactured. Usually the weight rating is based on all components involved and is placed by the manufacturer when it is built. I do know that you can reduce the GVWR on the ownership but the sticker on the vehicle remains the same.