Depends on what you’re looking to accomplish. If you just want lower rpm at highway speed, you may be happy with the TKX with 0.82 overdrive and your current rear differential gear ratio. You will first need to evaluate if your current engine configuration will be happy running at the lower rpm. You should play with some of the calculators available online to compare what you currently have and where you’re looking to go. This calculator is one of the more basic ones.
https://spicerparts.com/calculators/...rpm-calculator