I do not think there was a rotor specific to the A70.
When the B50 timing recommendation was revised a service sheet showed how to mark the rotor with the new position.
Below is from Lucas dated 1978, even lists the A70, showing only one rotor for the whole range, 54202275, which will be the stronger welded item. Lucas rotor part numbers confuse me, sometimes the number listed is for rotor with its keepers, which is different to the cast in number on the rotor.