I would worry more about exceeding the tires and/or the rear axle weight rating. If you are below that, then drive on. My F350 is only rated for 9900lb GVWR. It weighs 7800lbs empty. That leaves just 2100lbs of payload by GVWR. The rear tires are rated at a little over 6800lbs at 80psi and it just so happens that is what the rear axle weight Gross Axle Weight Rating (GAWR) is according to the sticker on the door jamb...
Now when you look up the specs on the Visteon 10.5" rear axle, they rate the axle for 9999lbs (or there abouts).
I have 94k miles on my truck and at least 50k of that is hauling a cabover weighing at least 3500lb loaded (never weighed, just guessing there). With the cabover loaded up for a trip, I am right around 11000-11500lbs. Which is above the GVWR, but well within the tires and axles. Clear as mud???
Again, JMHO, but as long as the tires and axle is not overloaded, you are fine. Keep in mind that almost every "overland" rig is well above the GVWR as are most RV'ers, but within the GAWR.
Jack