One of the original-equipment ignition switches works that way. Does the lock tumbler have a small handle built into it below the key slot? With the key straight up, the ignition is on. Turned to the right, the switch is "Off- - -unlocked". Turned to the left and the key removed results in "Off, switch locked". This was done so the vehicle could be operated without a key if desired. The 58 Chevy school bus I rode back in high school was set up that way.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!