NP208 cases are cheap and plentiful, I'd get another one and either swap the entire unit or just the guts...whatever makes more sense. I had a coworker once decide to weld an TH350 case that he busted on his pickup and it ended up being more effort that it was worth...and he was a proffessional industrial fabricator/welder. He sold the truck shortly thereafter so it wasn't his problem anymore.