On my 2011 Duramax I went from a 31.6” stock size to a 34” and didn’t notice a loss of power or towing ability towing a load similar to yours. I never towed super heavy, but I drug the trailer across the Rockies several times. This was with a 3.73. Remember, the manufacturer puts out different sized tires on the same truck/transmission/rear ended. They can vary by an inch or 2.
On another gas 3/4 ton truck I went from a 31.6” to a 32.7”. I haven’t driven it enough (it’s my daughters truck) to tell, but I’m guessing I won’t notice the difference and mileage may improve (it has 4.10 rear end).
I had an 89 with a 350 that was a high geared 3 speed to begin with. I can’t remember the tire size but I did notice a loss of power when sizing up a few inches. But it had less power and worse gearing to begin with.
