I was almost going to go down that route with the BDE 2.8, port / polish the head but I didn't want my car off the road that long waiting on workshops. The dimpling is interesting though haven't seen that done before, might watch a few more videos to see how they effect the flow. I would have thought a smoother surface would have achieved better results flow wise.
The zhorst I hit soap water and scotch brite and metal brush to start with, followed by a 400grit wet, then an 800grit wet, then a polish, then a quick wash to remove any excess polish. The thing was filth I could have spent all day on it. Come up better than expected.