For the heating of cast, it dose not do much good unless you can get the whole piece to or above 400 deg. You can also take and drill a small, say 1/8" hole at each end of the crack and this will not allow the crack to grow on you. Also a light peening motion with a ball peen hammer will relive the stress.
Another trick you can do is to use hard surfacing rods on the high wear areas. The type of metal in these rods is very hard and is used on construction equipment all the time. The weld will wear and keep the part from wearing out as quickly, prolonging the life of certian items. An example on a 4x4 would be the skidplates and so on.
