Differential Question

This might be a stupid question, but what the heck I'll ask it anyway. I have a 8 3/4 rear end. I also have a 489 case, nothing in it just the case. I also have gears that are for the 489 case. Here is my question is the actual differential part(sure grip, or open type) is that also case specific, like 489's have to stay with 489's, 741's with 741's etc. Any help would be appreciated!