[HO455]

There are several ways to do what you want depending on how factory you want the truck to look.

Replace the HEI harness with a points harness. This would be the factory correct style.

Or disconnect the HEI power from the firewall connector and add a new ballast wire to the existing harness. If you remove the HEI wire and re-wrap the new ballast wire with the correct harness wrap tape it would be the correct factory style.

Or add a ballast resistor to the end of the existing HEI power wire and run a new wire from the other connection on the resistor to your new coil. Mounting the resistor on the coil is a convenient way to do this. See photo. The ballast resistor in the photo has the flat terminal adapter that should allow your current HEI wire to hook right up.

Or leave the underhood wiring as it is and put the ballast resistor under the dash splicing the resistor into the ignition power wire from the ignition switch.