larger tires

Larger circumference (the distance around the tire) would make you go faster and farther than what the speedomter/odometer says. It may also reduce your acceleration a bit since it's like running a higher gear. Typically, you want to stay within +/- 5%. If it's an electronic speedo (very common, even if the gauge itself is analog) there are boxes that you hook in-line with the VSS (Vehicle Speed Sensor) that can adjust for the difference. Also, a taller tire will raise your center of gravity, increasing your chance of a rollover in an accident.

Here's one web site that calculates out tire size differences, at least for P-metric type sizes. For some of the truck inch-based sizes, there are probably truck-oriented sites.