Back to the OHC Pontiac.

You could deck the block & mill the head to get some sort of compression & get some quench going for you.

Unless the guy installing the bronze guides can drill them exact(not likely) you will have to get a valve job done.
I could be wrong?

Good luck.

BTW, your porting looks OK from the pics I can see.

MBHD
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12 port SDS EFI