The decision was made to go ahead and fix the other issues and make the castings usable.
This meant 13 more guides, machine the seats, flat mill the other head.

When I recut the seats, the 45 got pushed out quite a bit from how it was done originally, which required another angle be added below the bottom angle to help get a better transition into the bowl.
Even with the bowl cut, there was a pretty noticeable ridge where the casting ended and the machining started, so that was going to need to be blended in so they wouldn't lose flow from how they were before.

The other three exhaust seats on the damaged head were severely corroded.
Initially I was thinking I could just sink the valves a little and get into some new material, but after looking at them closer, and since some $$$ had been spent fixing some other issues, and the fact that the other head didn't have this problem, I just decided to replace those 3 seats.