Yes, Smaller tires will give more power, act like a lower gear ratio.
I have a 4:10 gear ratio in my ford, so I actually want bigger tires to get it closer to a 3:73.
In your case it is not a fixed number, the difference in speed variation will increase with speed. Example if you are reading 4mph wrong at 40, you might be 6 off at 60 you would have to do the math based on the circumferance of the wheels.
The smaller tire has a circumferance of 90.729 inches
The larger tires circumferance is 96.258
Your smaller tire will rotate 698.34 times per mile traveled
The larger tire will rotate 658.23 times per mile.
The truck will run a lower RPM at the same speed with the bigger tires, and can be part of the cause for the shifting especially when coupled with the extra power needed to turn the larger tires.
BLAH BLAH BLAH. There is a lot more, you can also just use the difference between the two sizes to actually determine how far off your speedometer is off at five mile per hour intervals, that will be simple algerbra.
Hope that this helps
David M. Beyer