You could make your own harness. You could connect it directly to the motor, or reuse the original molded quick disconnect plug, if it is still serviceable.
You would need to buy 25 feet each of black, red, yellow, grey, orange, brown and white wire. Create the harness with some of that black plastic split wire casings. Now butt joint it to the original moulded plug, or fins some way to route it into the motor cowling and connect it directly. Soldered bullet connectors would work OK.
Red is battery power, black is ground, yellow is starter solenoid, grey is choke solenoid, orange is ign kill wire to switchbox, brown is tach signal and white is ign power.
Solder the new wires (red, black, white, orange) to the original ign switch, and add a yellow wire from ign switch solenoid terminal to neutral switch, and connect a white wire from ign power to choke button an choke button to grey wire You also need a ign power wire to the tach connector.
You will also need to pull aground to the tach connector, plus the tach connection to the tach connector.
