I gota agree with Frank, I've fitted a bunch of petronic setups on British stuff. Four and six cylinder sports cars and the like. Often fitted on a car with solid copper leads and a dynamo (generator), not had any problems with them.
I'd like to add, I fit them because the customer wants them, personally if, I say if you can find quality reliable condensers, there is nothing wrong with a good old points setup.
Also, never had to increase the plug gap as one mentioned above. Increasing the plug gap and therefore the resistance in the high tension circuit, makes the liklihood of a crossfire or a spark jump to nearest ground increase hugely. This can wreck the distributor cap or caps and rotor and leads.
I can see no reason why the engine would run ruff with a stock plug gap unless the engine was running real rich or fat. If it is really rich, with a stock plug gap, if you pull the. High tension lead off the coil and hold it so its not quite touching the high tension terminal , the rpm will pick up a bit as the higher resistance (the gap you just made) makes a more powerful spark.
The flamethrower coil may say X kv, but that's what it's capable of if needed, if the plug gap is stock and the rest of the ignition system is up to par and the engine is in good tune, it'll never need the huge X kv and won't supply it. It's good for economy tuning though as you can run a real lean mixture and have the power necessary to fire that very lean mixture. I would not advise using a. 045" plug gap, it will bring with it reliability issues of the ignition system. There's a reason those HEI Ignitions have a trash can size cap, it moves the high tension terminals further away from one another, to iradicate crossfire with large plug gaps resistive leads, boots, plugs, big smog era open chambers, often nonexistent quench and high voltage.
Sorry for long post.
Martin