Tony has a good point about GVW Registration of a vehicle at a class lower than the weight rating; that's a great idea if it is legal in your State. However, you cannot change the GVW Rating determined by the manufacturer or the remanufacturer.
I've had toll collectors on NYC bridges ask my weight. When I said 6600#, they had me open the door to check the GVWR. A vehicle greater than 7000# in NYC is a class 2 and must pay higher tolls.
Highway signs in Illinois state a speed limit of 55 mph for 8000# trucks. The scales in Illinois require 8 ton vehicles to enter. GVWR or GVW, I think that's subject to interpretation of the DOT Officers. Iowa and Wisconsin also require 6000# vehicles to scale
Missouri, for example, allowed me to register a 9600# GVWR van at 18,000# to avoid the payment of sales tax. My reward for having done this, a DOT Officer later told me, was to pay annual taxes thru apportionment, log all miles, and scale in most states. It was a no-branier to re-register at the 12,000# level. This registered weight did not allow me to carry more weight than the legal or safe level of my GVWR.
My point: Registered weight is not necessarily related to Rated weight of a vehicle and State laws and regulations discuss them differently. Any owner contemplating raising or lowering a weight rating of any vehicle, should do so in compliance with the laws of their State government.
Terry