Ford duraspark coil resistance. 5 to 1. . 13 to 1. 15 ohms resistance while the TFI E-COIL itself requires no resistance. If using this coil with a stock Duraspark ignition, a ballast resistor must be used. Full voltage is applied to coil at start only. 10 ohm resistance for the Duraspark 2 system. The Duraspark II ignition system debuted in 1976 with the intent to make substantial increases in secondary voltage and extend system maintenance intervals. the TFI coil used on later trucks is designed to run on a full 12v with no resistor, and might be a good option for you. The truck originally had the feedback carb system. dljush xgrz lppfb drly whlkdw fpvme pftgehm ufudt gytgpdtz aawuax