Technical '54 Chevy 210 - ignition switch hole diameter

I need to order a switch for my '54. I'm at work and was hoping someone might know if the hole is 1" or 3/4"?

Thanks in advance!

 

Don't know the exact diameter, but it is definitely bigger than 3/4".
I have one off a later model chevy, fit the hole just fine and the lock cylinder was the same as well. The nut that holds it on is the same size diameter but the thread pitch is diffrent. The 54 had a very fine thread.

 

I think all GM dash mounted ignition switches use the same size hole,a 53 Olds switch fit right in my 37 Chevy.

 

Pontiacs used a bezel and the switch mounted like the chevy truck to a bracket