First, a factory installed (I believe) cylinder on one of the five 1959 rims, which I assume is a balance weight of some sort. If so, it doesn't say much for build tolerances back then!
Secondly, the position and shape of the engine hand crank handle hole in the front bumper. Horizontally, this is 25.5 inches from driver's-left end of bumper, 34.5 inches from driver's right (that is, looking forward). I don't know how uniform all bumper overall sizes are, but this is how it works out on mine.
