As long as you have a 4cyl third going in to a 4cyl housing and a v6 third going in to a v6/turbo housing.
A v6 third form your rear will not work in the front.
What do you mean by easiest way to regard this thing?

a v6 8inch 3rd member fits right in 4cyl housings. such as a 79-85 toy front axle.

i think your refering to 4cyl gears going into 4cyl 3rd member cases and v6 gears going into v6 3rd member cases. this last statement is general true but there is a way to interchange the gears and 3rd member cases. it has been done, do a search if you are interested in it. i believe it can be found in the toyota faq on pirate. i hope this helps.