Bear, I believe what he is saying is the total of the four rear tires has a total rating of 9,980 pounds.  That would be about right for an E load range tire - 2,470 pounds per tire.  And the LT225/75R16 with load range E is a common tire on Class C motorhomes.

jncrowe, you would likely need to upgrade your rims if you upgraded tires to a higher load range.  The rims have ratings too and they are usually rated for something close to the tire capacity.  It's possible that they are rated for higher, but then you might still be limited by the rim ratings even if you upgrade to a G load range tire.

Assuming you upgrade both tires and wheels, you would need to find the same tire size with a higher load range OR find a different size tire with a higher load range.  In either case, you would need to make sure the rims will work with your axle and hubs and you will need to make sure the diameter of the tires is the same or nearly the same as the stock tires.  It's certainly legal to make those changes, however it would be best to contact the chassis manufacturer to get options they recommend (sometimes the information is included in the chassis owners manual, but I wouldn't count on it).  If you make the change, you will likely exceed the Gross Axle Weight Rating (GAWR) and perhaps the Gross Vehicle Weight Rating (GVWR).

If the tires are overloaded, certainly there is a higher risk of tire failure and that is, of course, a safety consideration.  If you are unable to replace the tires and rims for whatever reason, keep your speed down.  Lower speeds increase the capacities of the tires, while higher speeds decrease the capacity due to the higher heat generated.

It's not an easy issue to resolve, and that's why we try to educate folks on these issues before they buy.  Best of luck to you.