Then again, it depends on the condition of your engine. Mainly the condition of the Distributor. If the shaft is too loose or warbled, if the lobes are worn, if the gear is loose. Rather than trying to fix it by putting a different Ignition System in, do an overhaul on your Distributor, THEN decide.
After you have done all of that and your system is tight and you have tuned it the very best possible, including valves, carb/mixture, etc, and its all perfect, THEN make the decision.
After doing all of that, it is clear that HEI not only gives a more precise firing of the coil, but does so at every RPM. This is possible because it uses a computer to 'learn' how your engine behaves at each RPM and adjusts the Dwell to compensate. It does this in milliseconds as opposed to not at all with a conventional system.
While this can be a very minute difference on a well tuned, adjusted stock system, it can also be a very major difference at different RPMs. This has been reported by the large amount of feedback I have personally gotten from Car and Truck owners of the era. The largest gain in performance is reported in 3rd and 4th gear. The computer is compensating for the differences in the drag of a loaded engine.
This is not to say that HEI is for you. A decent HEI system that meets all of your requirements can be expensive, while a pseudo HEI (Pertronix) can do the job for you for much lower cost.
Anyone who does not have HEI experience should not diss the idea offhand. I get testimonials on a regular basis that are clearly otherwise, but at the same time, I do not recommend HEI for everyone because you have to know the difference between a stock system that just needs a decent tuneup, and a person who knows what HEI CAN do and is much more discerning. Nothing wrong with Stock. Tune it up first, THEN see if you are still interested.
