Your foot is replacing the purple wire. With a standard starter, the purple wire activates the solenoid coil that pulls the solenoid closed to activate the starter motor.
Your foot stomp starter doesn't have a mounted solenoid. The foot stomp switch sends straight battery power to the starter motor.
The ignition switch only needs accessory, off, and run. In run, the HEI will need full battery voltage using a heavy 12 gauge wire. This means the ignition switch will also need a 12 gauge wire feeding it from the battery and/or amp gauge.
The purple wire can be removed or stored away under the dash. The start circuit of the ignition switch won't be used with foot stomp start.
The picture of the stomp start switch above has the small post on the side that provides voltage to the coil when be stomped on when using a points ignition system. This bypasses the resistor wire assuring the ignition has full battery voltage when cranking. When HEI came out, the engineers designed the start system without the extra wire to the coil and resistor wires. As long as your harness provides full battery power in the run position ( no resistor wire ), yours should start and run. HEI is not happy using less than 12 volts or small feed wires.
