oldtamiyaphile -- That story is probably the one about the college students' cut-down flat twin. I thought it's been posted here, but I can't find it.
Anyway, it was a bandsawn and rewelded case and bandsawn heads. The other trick parts are the camshaft and crank. They may have used a built-up roller bearing crank.
https://en.wikipedia.org/wiki/Volkswagen_air-cooled_engine#Half_VW
There have also been examples of VWs with one bank lopped off for a flat inline twin. Those aren't as successful.
Gary Emory also cut Porsche sixes down into fours. Don't know that they have ever done a DOHC flat twin, though.