It is about 6-7% over, static weight? There can be that much error in a mobile scale.
Other factors associated with that weight rating are ambient temperature and running speed, which combined with load contribute to raising tire temperature, the ultimate cause of failure. Run below the rated speed, you have more margin for contributions from overload, and heat coming from the pavement.
It is not something I see as a crisis. My rear tires run close to 100% load when carrying extended family packed for long trips, I run at 60-70% of the speed rating (means cutting that heat load almost in half) and check tread temperatures at every stop.
When replacing the OEM tires I upgraded to XPS Ribs for an extra margin on carcass strength (but they have a lower speed rating for extra tread depth). Silent Armor with steel carcass and an extra belt ply of Aramid, or all steel Duravis would be upgrades in other brands.
For the front, you can go up one tire size, at the cost of losing interchangability. Ford uses a larger 16" tire on a different wheel for single-rear-wheel E-350, higher capacity per wheel and tire than on the dually. Larger tire on the dually wheel, you would have to check out clearances for steering and suspension movement.
Also, despite what sticker recommends for front axle on E-450, you have a 80 PSI tire on an 80 PSI wheel, and you can inflate for load, up to maximum load pressure of 80 PSI. If you don't have maximum load, higher pressure reduces the contact patch, and on the front, handling gets looser.