little missfire help

The best way to determine if it might be mis-firing inside the cap is to check the "rotor phasing" with a timing light. Drill a top hole in-line with one of the posts in an extra distributor cap, to see the rotor with the light. You can find videos on youtube. Normally not a problem with factory distributors, only when you add aftermarket pickups like Holley XR700. However, Richard Ehrenberg sells an adjustable toothed wheel for factory distributors on ebay, so perhaps there is a problem to solve.

HEI is hotter than the factory Mopar ignition, since doesn't require a ballast and you can run a hotter e-core coil. You might notice an improvement with an MSD box. The very best ignition is distributor-less, single coil per cylinder, like GM LS engines or Mopar Hemi's. However, I know of no store-bought solution for our cars.