[Formulajones]

You can certainly trigger an MSD box with the HEI, so you have a soft touch rev limiter. You gain multi spark discharge as well, which I kind of like myself since my cars are a pinch on the fat side at 5,000 feet, it seems to keep the plugs a little cleaner compared to the cars that I don't run a box on. If you want to use the HEI I'd try to find a stock module.

I don't really like the MSD modules in the HEI's though. I had one that was causing the car to pop and bang horribly, and it was intermittent. Other times it would run fine. MSD tested it and sent a new one no charge and I never had a problem with it since. But I tend to shy away from that deal anymore. This was probably 6-7 years ago.

I do like the MSD boxes and some of the features they offer. The neat thing is that you can trigger it with anything, I even have one car here I trigger the box with a factory points distributor and that is by far my favorite setup. I run a digital 6AL on that one.
We run a couple of the MSD billet distributors that have been flawless for 25 years, and on one of those is a digital 6 box with timing retard, 2 step etc... That box is also about the same age. The other car has a analog 6AL and it's worked fine the same amount of time.

As far as the digital boxes go, it's like any electrical item, they fail at any time and there is no set time limit. Like I said I have one digital that is more than 2 decades old that still works fine. I also have a newer digital triggered with a points distributor that isn't a year old yet, but works fine. The beauty of that deal though is that if the box ever fails, I can swap a couple wires and drive away on the points

I will add however I recently installed a digital 6AL box on another car, triggered by the points distributor. Right out of the box it had a problem and wouldn't fire. I swapped a couple wires to run off the points, it fired to life and confirmed right away the box was faulty. I sent it back and it was replaced no questions asked. The new one has worked just fine.

Like I said, electrical stuff is always a crap shoot but most of the time you won't see a problem, it's not enough to worry about. As long as you have solid grounds and power supply.