tail housing

So i bought the m50d r1 with the tone ring just did the tail end housing on it with the speedo gear the thing is it has 3 spots to put it on the actual shaft is it for different gear ratios? or is it all the same mines about 10 km out roughly didn’t know which one just put it on a random spot...

for example i found an m5r1 from the yard that is 2wd and i have the tail housing from another fm146 4x4 can i put the mitsubishi tail housing on the m5r1? or the one from my truck that i actually would like to use that has a manual shift lever.