I replaced the lenses on my 1954 3100. I was surprised that the new lenses did not fit - the holes were spaced just a bit different. Turns out at some point a PO used 1956 lights instead of the 1954-55. You would never know the difference - the housing, diameter and appearance are identical, but the holes are not the same. Fortunately for me Grumpy's Truck Parts in AZ knew right away what was wrong, and replaced the lenses with the "proper" 56 lenses.
