I can help you but I'm not sure about the 1 wire alt, because mine was multiple, but I'm sure its a similar setup.
What I did to kill the alt was splice into the power sensing wire so if the switch were flipped the alt loses all power.
Depending what you for aux. elec. accessories (i.e. external fuel pump, e-fan) you can run them to the switch like I did. I know for sure you have to cut the power to the alternator.
So heres the wiring diagram I had for my stang.
Also what type of switch are you using? I am used the moroso super duty battery master disconnect switch.