I was thinking that surely at some stage someone made an aftermarket HEI setup to fit Lucas distributors.
Another possible option is a Scorcher Distributor - been ages since I dealt with them. They are based in Melbourne and make distributors for A and A+ Series (and many other engines) based on Bosch Dissy's.
Performance Ignition Systems is the company;-
https://performancei...m.au/p/scorcher
Lucas made an electronic module that was stand alone and you bought the pickup and trigger wheel to suit you car. I will have to look up the name but I doubt they would be available second hand anyway