It's ether not either but it could cause major damage if the air filter was dripping! That's beyond excessive. It's probably a good thing it didn't start. If the welder has a Murphy switch set up and it had an oil leak, it's supposed to shut down. If parts for the Murphy set up are broke, they need to be replaced with the correct parts, not something that will fit. That could be the exact reason it won't start.
Never heard of 350 Wildcat before. I'd guess the engine is a Perkins or a Continental as that's what Miller has used in Trailblazer 55D's that are 350/400 amp machines. They have also used other engines. Sometimes people with no experience with diesels or machines in general should REALLY get a manual and perhaps find someone with experience before they try to do anything with it. The poster may have just cost himself a few thousand dollars in unnecessary repairs.