I have a transmission case off an old John Deere tractor that is cracked that I am planning on welding. It is to large to put in my oven, 3' X 2', to preheat. I have welded cast iron before with good results with my mig welder but have always been able to preheat. Do any of you know of any welding sites I could get information on the best method to do this. thanks Bets