Broken bolt in thermostat housing….

Ok I friggin snapped the bolt that holds my water neck to my water pump housing. I'm apparently not a very good machinist, I tried using a bolt extractor kit for harbor freight and probably made it worse.

Any advice on getting it removed without buying a whole new water pump housing? My plan would be to drill out the hole larger and run a new bolt and nut to mount.

1964 Chrysler 300k with 413 AC is the car.

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