You can get a coil with a built in ressitor. that what i did when i had to redo something once never had a problem
Information about Ignition Coils - Certain ignition coils require an external ballast resistor (off any 1955-57 General Motors vehicle) or a full-length resistance ignition wire (off any 1958-74 GM vehicle) to prevent from putting too much voltage through the primary circuit and ignition points, which could burn them up. A ballast resistor or resistance wire is basically a voltage reducer that reduces 12 volts down to anywhere between 6-9 volts, depending on the load. (The ballast resistor shown here is the same used on the 1955-57 GM vehicles.) But if a coil reads "12 VOLTS" on its casing, then it has a built-in resistor. A resistor may not be needed with many new coils because most of them nowadays have a built-in resistor. And using a resistor doesn't effect the voltage output of a coil. It only prevents from burning it up, and it saves wear on the ignition points. The reason manufacturers don't install a resistor inside some high-performance coils is because these coils draw more amps from the battery. This causes the resistor to operate at a higher temperature, which could overheat and damage the windings within the coil. If you prefer to use a high-performance coil, when you purchase one, be sure to ask the salesperson if it has a built-in resistor or if it requires an external one. This is important for the life of the coil.
On the plains of hesitation lie the blackened bones of countless millions who at the dawn of victory lay down to rest, and in resting died.
The only thing that comes to those who wait is old age
Go forth and be a force of the awesome!