Tire Max Load rating and GAWR

is it a 5th wheel or a trailer?  if your towing a trailer you are mainly concerned with the axel weights, so you do the front axel independent of the rear, so all that weight is being added behind your rear axel so it will all go on the rear and the fronts will get a tiny bit lighter, and by using a equalizer hitch you can put a tiny bit of that weight back on to the front's.

if its a 5th then 99% of that weight is going directly on our rear axel if it is set up normal and the fronts don't really change much at all.

My question to these questions is, "WHAT" or "WHY" is your RA rating only 10500? Is it springs? axle itselfs rating. or rims or tires? Tires can be multiple issues. THe manufacture may use a tire that is good to the 15000 as you note 4 are good to at 80 psi, I am assuming. OR< they could be rated to 10,500 if you only have say 60 lbs in the tires! In this case, it will not matter if you tires are E/10 ply rated, or D/8 ply rated. That tire size at 60 lbs is good to 10500 total! 
At the end of the day, it is better IMHO to have a bit more tire than spring, rim or axel rating. I've had more issues with tires at max ratings than the other parts I've mentioned. 
Also, that size tire, ALL BRANDS and tread designs have the same max capacity. WITH THAT said or typed in this case. You will find some designs of tires, WILL be better for heaviest of loads ALL the time. Especially ones with steel sidewalls and tread, vs polyester sidewalls and steel tread compounds. Issue with these two designs, is the all steel case tire will weigh upwards of 10-15 lbs per tire. This extra weight does take some HP, along with an MPG drop. Amount will depend upon the motor and drivetrain you have. Ive had .5 mpg with an 05 DA DW going with Toyo M55 vs std Toyo AT tires. Both 215-85-16 LR E. My 1500, the 285-65 LR E tires are 15 lbs heavier than the stock P metric XL 265-65-18 tires. I lost close to 2 mpg, some due to weight, some due to an extra inch diam or 1/2" active radius. Being as the new ones are labeled AT, they really are a true mud/traction tire IMHO vs the stock ones being a HWY tread. ALL of these issues can make or break how a tire works or does not work etc for you. 
My case, two of the tires you are looking at, or the two of the 285's I currently have, will handle the 8000 lbs of GVW my truck maxes out at. I run both tires at 35 front, and 30 in the rear. Otherwise the middle 9 of 11" of tread are in contact with the road at 80 lbs of PSI. 

Probably more info than you need. Your tire capacity is plenty/OVER for the axle rating!

Marty

10500 gawr will be the lessor of a wheel/tire rear suspension/rear axle assy regardless of over size tire capacity .....10500 rawr will be your max rating.  Higher tire capacity is nice for more tire safety reserve.

 I've towed for a living and I would recommend dropping by your local state troop  and ask that question.  A rv forum is a poor place to ask about what is my trucks 10500 rawr max load limit will be..