As per me ONT SF trains or trains that can be maintained with 2-3 rakes , having CC of 22-23 coaches and having a good patronage all round the year will be the Best choice for considering for LHB coaches.
CC reason being as of date LHB rake comprises only 20 coaches, leaving 2 EOGs aside. If a 24 coach ICF train is converted to LHB, then there will be a drastic reduction in seating capacity (even though higher capacity per LHB coach is taken into consideration).