HEI in a Mopar?

Aw shucks Tom, thank you.

There are a bunch of aftermarket parts that come with HEI parts in them like "Ready to run" distributors as well as aftermarket HEI modules by Accell that replace points and OEM electronic equipment.
The ones I build use the OEM electronic distributor, but everything else is replaced with the HEI stuff prewired and ready to connect up.

Most of the trouble shooting of HEI stuff you are seeing on the board is of people who decided to build thier own and missing something like reluctor gap, or power supply to the HEI coil, or even a good ground.

This is mine installed in my Dart and I have been running it for over a year now, and it's been flawless.

As far as I know there are no drawbacks, but plenty of positives.
Better starts (hot and cold both)
Better gas mileage
More power
Smoother idle

Since the spark is so much hotter and longer than stock, you can run a .045 plug gap and this is where the HEI gets it's performance advantages from.