Yes, the carriers and gears will interchange between front and rear thirds.
From what it sounds like, you are wanting to reuse the existing pinion that is in the front third and swap in another ring gear. That is a big no-no. Gears are made as matched sets and should not be mixed and matched. I'm not saying that it wouldn't last the life of the samurai, if you mixed and matched gears from 2 different thirds, I'm just saying that it is not recommended.
Also, if you remove the pinion flange, you need to make sure the pinion nut is put back to exactly where it was before it was removed. That way your pinion bearing preload stays exactly the same as it was before you took it apart.