Cooper makes an AT3 XLT in 295/70R18 that has 4080 lbs capacity. It is only 1 inch taller than the stock 275/70R18’s (3640 lb)and is almost negligible difference on my speedo vs gps. Many others make this size also that sticks to 80 psi.
So for my fifth wheel the extra 880 lb capacity theoretically translates to 4400 lbs additional fifth wheel weight at 20%. Of course I will never use that additional capacity but it does give me better wear characteristics since I’m running around 6600 lbs on the rear axle.
The first set of Firestone at tires lost a lot of tread on a trip to key west towing my fiver. The Coopers have a 60,000 mile warranty plus they are much better on the farm.