No activity here for a few weeks, so I thought I'd add the conversation. After I converted over the the Lucas DKX2A distributor, it was natural to add a key switch.
With the stock Lucas mag, it is still possible to add a key switch if the switch could be made to lock in the closed "on" position. Connecting that switch to the optional Lucas cut-out cover on the mag would be quite effective. Essentially, a keyed kill switch.