These 4" wide sills are genuine Rover replacement parts with 6 vents and are for MK3 on saloon. Non Genuine is
MS63R Most/many 1970 cars and Cooper S mk3 had 4 flutes.
They will fit MK1/2 but not original fitment. Closest and best MK1/2 panel compared to this is
MS30R with 4 vents/flutes which is a superb panel.