I’m assuming this is a 5.3 TB with the 9.75” rear end, I think the only gear option is 3.42. If you move up to a 9.76 axle, those had 3.73 gears with the diesel off road package, or the new diesel max trailering package.
Even the 6.2 max trailering package only received 3.42 gears, only way to get 3.73 is with the diesel.