from what you describe, I would suggest 3.73's. trucks not lifted and just going larger wheels. are you going larger tire hieght or just increasing rim diameter and going lower profile? If you are staying at a factory tire size the 3.73 will increase that low end grunt for the get up and go without making your highway rpms too high. you will still need to adjust your speedomemeter with a gear change. May be able to go with a programmer or even better a custom tune. this will be cheaper than a gear swap as well.