Rear end

Put the rear of the car on jack stands. Check the rear ends bolts for a metal tag that will state the ratio within. If it is not there, continue with the following.

Chock the front tires, then the trans in neutral. Rotate the rear tires and count the driveshafts revolutions. This will come up with the approximate gear ratio. A white out pen is good to mark the driveshaft.

Or, take the cover off and service change the rear end oil.

To swap gears and the differential, parts are available. Suregrip units are reasonably priced as well as the ring and pinion.

On we all know what the ring & pinion ratio is, true & better suggestions can follow. FWIW, I also will suggest a upgraded torque converter well after the gear swap, if the new ratio doesn’t do it for you.

Considering you said it is a daily driver, I wouldn’t use a ratio above 3.21/3.23. I’m also assuming you may see some interstate driving.

Where in Fl. are you?