A friend has these assembled Stage VI aluminum heads with MW ports. That family of heads was rather hit and miss but neither of us can find any info on this particular casting.
They seem to be as-cast.
He picked them up from a club member who was trying to liquidate stuff before he passed. Any info about them died with him.

Do any of you know about this casting?

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We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon