Starter differences

[80stech]

I think I need to do the coolant pipes on my wife's 2005 X3 2.5 L M54 and thought I would do the starter at the same time. I did both on my 2004 X5 3.0 L M54 a while back and my plan was to refurbish the starter I took out of the X5 to put into the X3 when the time came, but now when I checked into it a bit more there are different part numbers listed for each, anyone have any experience with what the difference is ?? Thanks!