Holley Hemi Coil Harness 558-311 | Chrysler has used two different coils on the HEMI engine series with 2006 being the year that the change was phased throughout the truck and car line. Fortunately the two coils are very different visually and makes for a simple review. If the coil requires spark plug wires, it is the early coil. If the coil does not require plug wires and simply has two boots that connect to the plugs in the cylinder head, it is the later coil. View the image gallery for images of both types.