Being an “early HE”, I presume the car has Digital P EFI? There is no trigger board inside the distributor? I didn’t realize the Opus ignition system hung around that long.
You’re describing the Opus ignition system. They were never good, and at this age they’re likely to prove more trouble than they’re worth. As Ed suggested, updating to an aftermarket ignition system is one possibility. Another is a replacement scheme utilizing the later Lucas CEI ignition packaged in an amp that LOOKS like the Opus amp, thereby maintaining the original underhood appearance. Finally, the car could be simply upgraded to the Lucas CEI by replacing the distributor with one from a scrapped car. The Lucas CEI is, in fact, an excellent ignition system, its one noteworthy shortcoming being that the centrifugal advance mechanism tends to seize up – but that’s true in the Opus distributor as well.
Or one could go completely overboard and go with a modern aftermarket EFI/ignition controller like a megasquirt.