The new tires should e about 1.5 " taller. So yes the speedometer will be off, but only by about 3 mph at 65. Also there will be a slightaccelleration decrease due to the new height.

 

Is it absolutely necessary to have my speedometer reset because of the size difference in tires?

And if I call the dealer, what exactly do I want them to do? Do I tell them that I want the speedometer recalibrated?

what's the best way to make up for lost acceleration? Will a K&N Intake and flowmaster dual exhaust do the trick?

Sorry for all the questions. I'm new totruck modification.

 

No you don't have to have the spedo fixed. Hunt and I both have larger tire and never got ours done. To get the power back yes exhaust, intake, filter or any of the free mods listed on this site will get it back for you.

Your milage may drop off by 1-2 mpg as well depending on your gearing.