First if you use a 4 pin ECU box then you can use a 2 prong ballast. The .5 ohm ballast is to the coil and the 5 ohm was for the auxilary run circuit to the ECU that was ign run voltage thru the 5 ohm side to the ECU. This 5 ohm auxilary ign run (its not a start circuit as many think) is the circuit that is eliminated on the 4 pin ECU and you can just leave that side unhooked and use a 2 prong ballast with the 4 pin ECU. Ron