Compatible with GM HEI distributors; GM Dual connector coils mount directly in place of the factory coils and accept the factory connectors. Spark energy is increased thanks to improved materials and windings that were spec'd by MSD engineering.;.
While there's usually nothing wrong with a standard grade AC Delco ignition coil, I do find some very slight performance improvements from my MSD components. I believe that they take a little more care in their winding process, and perhaps the quality of wire used. I live at high altitude so any small improvements in ignition response is worth the cost of the improvements.