Rearend

Ring Gear – 9″ OD – Tooth count 39 – 10 bolt holes – 7/16″-20 RH threads Pinion – 28 spline shaft – Tooth count 12 – 3/4″-20 RH threads

The difference between a 3.25 and a 3.00 gear ratio is less than 8%. If you have a mechanical problem with the rear, changing the ratio may make sense. If there is nothing wrong with the rear now, getting larger tires may meet your needs and save you some money.

Here is a good site to compare gear ratios and compare tire sizes. https://tiresize.com/gear-ratio-calculator/

Count the teeth on the pinion gear and multiply by 3.25 to find the number of teeth on the ring gear. Let's say the pinion is 16 teeth. Then 3.25 X 16 = 52. So your ring gear would/should have 52 teeth. That's just an example how the math goes. But I agree with Gary. Why mess with it? Parts are very expensive too.

Count the teeth on both gears to confirm you really have a 3.25! If you want economy and low gears for towing you should look into a 5 speed conversion in you have a manual transmission or a modern 4 speed auto box with OD if you have an automatic.