I WORK AT A FORD DEALERSHIP IN DES MOINES THAT MOSTLY WORKS ON SUPERDUTYS AND POWERSTROKES,I HAVE EVERY HEAD CRACK CHECKED THAT I HAVE OFF AND ABOUT 75-80% ARE CRACKED EITHER AT A COOLANT PASSAGE OR BETWEEN THE GLOW PLUG HOLE AND A VALVE,I THINK EVERY 6.0 CYL HEAD THAT IS REMOVED SHOULD ALWAYS BE CRACK CHECKED WITH NO EXCEPTION