81 300sd how do you know which power steering seals for pump in part store.
 

i see three different sizes for the front seal, is there a difference in the pump itself by brand or do i need to pull it to find out what size? this is in the peach parts store

There are at least three different types for the Vickers pumps and then there are the ZF pumps too...

...I think you need to find a supplier who can check for the correct part via your VIN. That's what I did for mine - I went to the dealer. So the answer could be to contact this site's sponsors.