Hy Alex Arrow, depending on which type of two speed rear axle you have, there may be some gear options available. Gears from a Diesel truck are usually lower numerically and result in higher speeds when installed behind a gas engine. How is your two speed shifted, mechanically, electrically, or vacuum? If you could post a picture of what your differential looks like that would help us identify it. When we talk about getting higher road speed out of our Big Bolt we must discuss the fact that these trucks were never designed to go more than Fifty miles an hour (the common speed limit when they were new), upgrades to brakes, tires, wheels and steering should be made to keep everyone safe at speeds above fifty. Ed has made an excellent suggestion for a newer Dana axle with more ratios available, it will most likely come with better brakes, possibly even disc brakes if you find the correct one, that would be a win win for you and those on the road around you. Hope that helps.
