Whats easiest to change back axle gears or just change the entire back axle
Buy the desired ratio ring & pinion gears & have someone set it up for you. The gear clearances are tricky. THEN you can re-install the rear axial center section. Note: high numbers are lower ratio like 4.56-4.88 for drag racing & lower numbers are for top speed on the highway like 3.23. A complete rear end swap is definitely more expensive.