8 3/4 diff

Hi all, I know there are allot of smart guys on here and hope someone can give me some info. I believe there are 2 different 8 3/4 differentials, large and small stem pinion. I would like to know how to tell the difference. I have 72 Duster with #'s matching 340 & 4 sp. gear ratio is 3:23. Not sure which one is in the car. Can someone tell me the difference?
Thanks..............Dale