The ever popular "Sports" high voltage ignition coil.  Suitable for all British cars without a ballasted ignition system.

Spark plug gap should be increased to take advantage of the extra spark voltage this coil can deliver.  Cars equipped with moderately upgraded ignition systems can open their gap to 0.035-0.040", cars with 123ignition distributors or similar high end ignition systems can run a 0.040-0.045" gap.