it's only going to be a negligible difference, the factory tire should measure out at 34.36 inches, so your only adding .63 inches on paper. If your real **** about it, mark the factory tire with an arrow in chalk on the side directly at the bottom and make a matching mark on the ground so they line up, roll your truck forward until it has made a full rotation and the arrow on the tire is once again pointing straight down. Mark this on the ground and measure between the first mark on the ground and the second. This is the effective diameter of your tire, which is used to calculate mileage, speed, MPG, etc. Do the same with your new tires and figure out what the % difference is from factory and new tires. If the replacement tire is 5% bigger, then your speed will read LOW by about that much, as well as odometer, etc. If it is 5% smaller then all your readings will show to read HIGHER by about that much. Again, in this case it shouldn't be by much. If I'm putting bigger tires I never adjust, because then I record less mileage on the odometer for trade & warranty purposes!
It could actually be much greater than what is on paper, depending on how accurate manufacturers measurements are (they frequently aren't!) and depending on sidewall sag
