1950 FC293.
Do you have a foot start or a solenoid start?
1. Your first question was answered by Kevin. Buy that switch and buy the tumbler and keys for it. Sounds like you ordered it, good.
Don't need it for a start up.
2. You say you do not have a 6V battery.
3. Buy a 6V battery or convert to 12V. Do one or the other.
If you don't have a 6V battery, want to start and run on a 12V battery and you have a foot start, you will have to buy a
12V coil, a
ballast resistor and a foot start switch with a
side terminal. That's half way to a 12V conversion. So advise what you want to do and I will help.