How to repair valve guide boss

Indiges said
Hi, I just came across this thread and I have a similar issue (as per photos).

So as plainly as you can explain it, what's the best way to repair these?

The guy rebuilding my engine was going to scrap my heads and use replacements, but I think my existing heads are a higher spec.

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If a shop was going to scrap your cylinder heads due to those valve guide cracks, that shop is telling you they are either
1) don’t have a clue what they are doing
2) only after your money
And in response you should take your work elsewhere.