Turned out to be not as dire as I originally imagined.

I didn't check the bolt size and bought stuff for m7 threads. I drilled it and tapped thinking it was strange that the seized bolt was bigger. I was able to knock part of it out with before drilling slightly larger and tapping with m8. Since the first couple of threads were clear I think I lined it up pretty well.

Sometime later today my coworker should come over and help me with the last one by welding the nut to the seized bolt. Again I'm hoping the heat helps it break loose and the nut gives me something to grab on to. I'll switch out the paper towels for aluminum foil to prevent a fire.