We have a MBE450hp, 3:58 rear end, 22.5s. We seldom run as fast as 65. We tend to run in the 57-62mph range. We are grossed at 48,000. We have an EatonFuller 10sp auto-shift, 3 pedal model. We like to keep the rpm range between 1200-1400, no higher. 1375 or so is 62mph for our truck.