Wow! This whole issue is sorta screwed up.
In the car rules, 2.L, it says that they have to be 3 inches high. Nothing about a 1-inch stroke. If there were, an 8 would be solid from top to bottom.
And the 3-inch rule doesn't apply to the class designation. But you MUST have a class designation on your vehicle.
In the motorcycle STREAMLINER area, 7.H.16, it says you you gotta have a minimum number/letter area of 10 inches by 16 inches -- but doesn't say what you gotta do with it.