Flickering head lights, what am I missing

OK you are only showing 3 terminals on the disconnect. Can you detail how you have it wired now. I recommend some sort of relay switched by the (normally 2 smaller) disconnect terminals. You can use that relay to break ignition, or 12V feed to the VR, or in case of EFI the fuel pump relay. Or even a combo of 2 or all 3 of those. Obviously a carbureted engine, it would run for a time on what is in the bowl