I've done the cutting torch bit before, but only on crawler tractors, like Cat bulldozers, and it was not in a blind hole. The bolts that hold the track tread plates to the track chain were almost always stuck beyond removal without tearing up the bolt heads, due to impacted grit. We'd tear up the bolt head, then fire up the cutting torch, doing a long preheat, and when you hit the oxy, it blew out the bolt and left the threads almost clean, nothing a chasing tap could not handle.

Not responsible for advice not taken...