This is the starter half clamp that holds the starter drive to the side of the bell housing.  There are 2 clamps required per car.  Sold each. 1945-1955 Silver Wraith, Mk-6, R-type, Silver...

This is the idler gear for the starter motor drive. The driven gear is RD7205. Note: This is factory new old stock piece from the factory 1956-1958 Rolls-Royce Cloud I & Bentley S-1

This is the original style push button starter solenoid that is mounted to the frame (engine area) If you want the modern style see RH8312 1946-19

This is the modern solenoid type starter switch that can replace the original push-button starter switch (UD4181). This unit does not have the push-button.