Dik:
Assuming you are still interested..., Hokie bumped my interest...., and left me a green star.
You may want to contact various crane manufacturers or go to the AREMA (American Railway Engineering and Maintenance-of-Way Association, the old A.R.E.A.), or the AAR (Association of American Railroads) they will have complete specs. and info. on available rails. The ASCE 40 is indeed one of the lighter crane rails, it is certainly not used on the railroads.
My specs. and info. on the subject of rails is so old as to be almost useless for really answering your question directly, if I could even lay my hands on it quickly. Although, the only things which might likely have change would be steel chemistry, mechanical properties, and the latest treatment methods.