The original WW&F had some 60-pound rail. In earlier years of the rebuilding, lighter rail sections were used, but more recently, 56/60-pound rail has become the standard for the main line. It's heavy enough that maintaining line and surface is not a problem, but at the same time is light enough to be handled without heavy equipment.
If anyone out there knows of any quantities of 60-pound rail available, we'd love to know about it, too.