car alarm for a 6 volt system??

My dad just bought his dream car, a 55 ford thunderbird. Which is currently on its way to the islands. Question is, i have been searching for a few hours to find a car alarm for the 6 volt system in the thunderbird. He really doesn't want to convert to a 12 volt and keep the car just original? any ideas? thanks in advance..

 

put a kill switch on it.i hate car alarms!!!

 

Pit Bull, Male, Hook the 6 volt to his nuts

a kill switch is way easier to feed