The original resistance wire, connected to the (+) coil terminal (crimped together with the yellow wire), was a cloth-covered white/red/black wire that goes back to the inboard half of the bulkhead connector below the master cylinder; that's the switched ignition feed to the coil from the ignition switch. That wire needs to be replaced with a length of regular 16-18 gauge wire to feed a full 12 volts to the Flamethower coil.
Leave the yellow wire in place - that feeds power to the coil direct from the starter solenoid only during cranking.