2 SOLENOID SYSTEM
There is a 2 solenoid setup posted in the following link that can be used. Technically it is a 3 solenoid system if you're counting the starter solenoid. All you need are the two solenoids, an on/off toggle switch, some heavy gauge wire, and possibly a new 2 position key switch for the ignition circuit.
http://www.buggiesgonewild.com/gas-h...-r-switch.html
I've attached two illustrations on how that setup works.
The first attachment shows what terminals are connected within the solenoids when activated and not activated. This can be used to test the solenoids. You have to have continuity and no continuity as shown in the diagram or this wiring setup will not work. Make sure the bodies of the solenoids are grounded.
The second attachment (gif) shows what happens with the starter circuit when the toggle switch is turned on or off. If you want your reverse buzzer hooked back up, just tap into the wire after the toggle switch.