Is your block aluminum or cast??? I have seen some cast block that were welded and or brazed over the years. The trick is you got to be really good with a torch and/or a welder. I have seen guys weld cast with a stick welder and use nickel rod. I've seen guys weld it with a wire welder and use stainless wire. However, these guys were really good at what they did. I had a guy weld some busted cast on the knotters of a baler once and that worked. He was good, been welding 30+ years. I could not have ever done it. You might see if you can get a block from an ag salvage yard, or find the exact same tractor in running order. Then you could use the "broken" tractor for parts. That is a farm trick special in the midwest.