The early 1/4 rod operates with a ball inside the button in the centre of the pressure plate. On the later 5/16 rods there is no ball inside the button which helps the plate to lift squarely. A 5/16 pressure plate ought to be easy enough to find if you want one.
36 4G, 37 VH, 53 ex ISDT KHA (project), 54 KH(A), Healey 1000/4 (project)
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.