Ring and Pinion change

I have a 2019 Toyota 4 Runner TRD 4x4. It has a 3 inch lift and 295 55 R20 wheels and tires on it. I want to change the front and rear end gaers to improve the torque and help with the bigger tires and wheels. Where is the best place to buy the parts for this job?

 

I'd check out the popular ones, just search gear and see who pops up
-Revolution
-Yukon
-ECGS
etc.

Probably gonna need at least, front and rear:
-master install kits with bearings and shims
-ring and pinion gears the size/ratio of your choice

If you install it yourself would be awesome if you make a DIY
Some people do it themselves, others pay a shop/or source pre-assembled third members to bolt in and return their original as core