what is a 200mm dif

like said in an other thread Im about to buy 1994 ram van

Id called the dodge dealer in town and ask what is the dif

the answer was a 4.10 gear and a 200milimeters dif

I ask him what the hell it is and he couldnt answer me
it look like a dana 60 but I know there is also a dana 70
that look like a 60 and it aint good for us

I know I will need to cut it but at 500$ for all van it aint to expensive