How does the steering column mount?

I have an all original, numbers matching, 1969 Formula S, 383, four speed Barracuda. When I bought it, some parts had been removed. They were all there and came with the car but I did not get to see the steering column mounted in the car. It has a plate attached permanently to it and the plate has 3 holes about the size of a quarter. Obviously a standard bolt won't work.
My question is, does anyone know what kind of hardware is used to attach the steering column to the firewall and do you have any pictures. I believe the plate goes inside the car under the dash with a white foam gasket between the plate and firewall and the bolts go through into the engine bay but what fills the large holes in the mounting plate? Any info or pictures or both would help so much. Thanks.