Are you doing all new bearings? Will you supply them? IIRC, TIMKEN is the original supplier. Try to find US Made versions. They are still available but you might have to work at it. You will need new pinion seal , crush ring and new nut. Will you supply those as well? Everything will need to be re shimmed as well. It could be a couple of $100.
I ran a car to SAAC 35, 2000 mile round trip. I swapped out the 3:89's and put in 3:00's. It sure made driving the interstate nice. They are still in the car. If you are not turning 6K, burning rubber and drag racing, the 3:00 gears are faster off the line and are little more fun driving around.
Best of luck
Cory