Jerry,
The only lamp listed for this application in the old green TRF catalog is for the 73 - 76 cars after commission number CF1. Their part numbers are 219139 for the lamp and LULL8286 for the bulb. I did not check availability.
I think this change coincided with the moving of the ignition key from the heater switch plinth to the steering column, but would not bet the farm on it. . . .