I could be wrong but I'm thinking on a 951 the oil pump is on the other side of the engine, which means the shaft would turn in the oposite direction. So the pumps would not interchange. Does the pump and shaft have a part no. if so check to see if its the correct part.
This could be a big mistake if its the wrong pump.
These pumps rarely need replacing because they are self lubricating, are you sure you need a new one?
Lou