Top off your Ford or GM ignition system with these great new replacement coils. The blaster TFI and GM coils have MSD Performance with factory style housings. MSD designed these coils by combining our blaster coils experience with E-core coil efficiency. Each coil has a unique turns ratio plus there is lower primary resistance than the stock coil. This all amounts to a bolt-in. Replacement coil that produces more output voltage. The coils will work with stock ignition systems as well as MSD equipped cars and trucks. Installation tip: if you plan to install an MSD Ignition with your blaster TFI coil, use a PN 8874 harness for a direct plug-in. Installation. For the blaster GM coil, use a PN 8876 harness. Also available blaster Ford TFI coil PN 8227.