To me it looks like it was in a puddle outside and froze. Yes it could be cast iron welded, but to weld all those cracks is going to take a lot of time. The problem is the weld area has to be preheated and then cooled slowly to prevent cracking at the edge of the weld. All of the crack has to be ground out or the crack can start to propegate again. In my opinion the cost to repair will be as much as buying a good core 340 engine.
