I'll wing it from a wiring diagram:
You'll need to focus on the power connector (two wire) for the old Duraspark box. Red is the correct ignition feed on at start and run, white is on at start only. I would use a relay on the red wire to feed power to the new module.
Remove the "I" connector from the solenoid and tape it up. Remove the wires from the coil and tape them up. Remove the coil. Remove the three-wire connector from the Duraspark box and tape it up. Remove the Duraspark box.
Follow the install instructions from the HEI kit using your own new wiring. You've bypassed the ignition signal for the MCU and it will never know the engine is running. Removing anything else is optional.