If you have the spider, and I think you said you did, that should tell you the diameter of the wheel. The wood wheels I've seen, vary from about 7/8" to 1 1/4" finished. I don't think that anyone would give you a bad time about the wheel thickness, also, depending on what the ends of the spider look like, you might have a hint right there. The Model T spiders have a curve in the end of them, that matches the cross section diameter of the wheel, I'm not sure about the Chevs, as I don't have one to look at.
