This is correct. It depends on the ign system which many times means which coil and ECU is also used. Most units that have everything in the dist like GM HEI use a simple 12 volts to feed it. But some electronic units with separate ECU units may use a ballast. The factory Mopar electronic ign used a ballast and so did the factory Ford units for some years when they first came out around 1975. I believe Ford called theirs Dura-Spark and it still used a resistance wire in the wire harness to the primary side of the coil. Also most GM and Ford point systems used a resister as they had a resister wire in the primary wire harness as most think Mopar were the only ones to use a primary resistance since Mopar used the ballast mounted on the firewall. But the Mopar ballast can change ohms a little by temp where I don't think the GM and Ford resister wire changed ohms with temp.


Bottom line is I don't think you need a ballast but your unit should have had some paper work to tell you what they call for. Most if not all MSD units do not need a ballast as the MSD box controls both sides of the coil since its a low speed multi-spark. I use the MP orange ECU and I don't use the ballast because I don't use a stock coil as I use the older Acell Super Coil which had a slightly different ohms then the stock dist so it has a different current draw in amps and don't overheat my coil or ECU. Good luck with yours , Ron