Daniel, I'm not positive on this but I don't think the trucks came with a clock.... but I have read here that some folks used a clock out of a 37 or maybe a 38/39 car. I think those were "in the glove box door". Soooo, maybe someone switched only the glove box door or cut it and put a clock in it.
Does the hole look factory??
I'm sure someone else will straighten us both out on this!!!
As Tiny suggest, a picture would be great.