Please learn to use the search function, you have asked a couple questions that there is a wealth of knowledge on already. If you need something clarified or can't find what you are looking for post away.
To be a nice guy -
Yes it possible, both front and rear.
ARB Air Lockers or Harrop (Eaton) E-lockers are your options.
In theory you could retrofit a Toyota OEM locker but to my knowledge no one has done so and I wouldn't bother due to cost/complexity.