Contributor: F. Navest
The original LUCAS 78106A sparkplug caps were original wear on 3 synchro cars, (i.e. during the production of the 18GA & 18 GB engines). They do, on the other hand, cause radio interference that was difficult to suppress properly. The technology involved with these plugs and cables was outclassed.
The state of art technology in 1967 meant that the copper core cables had to be replaced by silicone cables, which have a degree of internal resistance that surpasses the interference to radio and TV equipment.
These early 60’s Solid copper core High Tension cables in combination with LUCAS side entry distributor caps and LUCAS sparkplug caps last forever, however. I am not sure how long the Ignition Lead Spacer and yellow identity markers were maintained. I have the impression that the Spacer as discontinued in 1967, whereas the markers were probably continued till 1969.