Actually, Rail coach factories be it Perambur, Rae Bareli or Kapurthala deliver LHB/ICF rakes to Zonal Railways on a First cum First serve basis. I hope that ER which has suddenly come on an LHBfication spree considers trains like Amritsar Mail, Himgiri Exp & Doon Exp. The Kalka Mail may need to wait since it undergoes complex rolling stock activities like attaching/detaching a 3rd AC coach between Howrah and Mughalsarai + its AC coaches don't seem to be arranged in a single set between the Non-AC ones :)