Here's some information concerning the external floppy drive connectors as used on the 600-series and 365XD systems. There are two different connectors used between these systems and they are not interchangable.
This is a picture of the end of a 600-series external floppy cable, showing the overal width of 0.67" (17mm).
This is a closeup of the 600-series connector.
This connector is what plugs into the external floppy port on the back of the 365XD. Overall width is 0.8" (20mm).
365XD cable closeup.
This is what plugs into the back side of the 10H4056 External Floppy Drive. Width of plug is 0.83" (21mm) and is about twice as thick as
the connector on the other end of the FRU 74H0219 cable.
Closeup of connector that plugs into the 10H4056 drive.