Tune a stock mandated 2350

[BrandonOlsen]

So I have decided that in March I’ll be replacing the rearends. Replacing transmission to a 18 speed (currently have a 9 speed that was converted to a 13 speed) and replacing clutch. My question about the rearends as rawze suggested to go with 3.90s or 4.10s what rpm’s would I be at with certain speeds ? My main speed is usually 58 or 68 but there is a good amount of time where I have to be able to go 75. Want to do this early March as I’m going on vacation for a week with the family. I’m 18 hours from Atlanta and 13 hours from Detroit. Any GOOD shops maybe closer to the Iowa area? I’m no completely set on not taking the truck to Atlanta or Detroit but would like something closer . Also usually always 90k plus gross. Also currently I have inter axle Diff lock, what would it take to have full lockers ?