There's always light at the end of the tunnel, sometimes it's just farther away than we'd like.
Not tractor related, but applies to this situation:
2002 Toyota Tacoma, started to misfire badly. I narrowed it down to #3 fuel injector. Easy job, right? Well, both the bolts that hold the fuel rail in place snapped off dead even with the threaded holes in the aluminum head.
Galvanic corrosion is a serious pain. Bolt extractors stalled my 19.2v cordless drill, and my corded 3/8" drill. I didn't want to risk snapping the extractor off in the hole I drilled through the leftover bolt, so I kept stepping up bit sizes until all that remained were the bolt threads stuck in the threaded bung.
It was a smooth hole, but I could just barely see the outlines of the threads. Tried a thread chaser but it wouldn't grab, tried a tap, it grabbed and worked it back and forth until all remnants of the bolt were removed. Followed with the chaser, some new SS bolts with a liberal amount of anti-seize. Then I had to repeat the process for the rear bolt!
It was a 25 minute job that turned into a 4 hour job.