The last SWB 911 I raced with PCA from 2009 to 2012 was a 1968 911L that I modified to be a 911TR-look car from 2005-2009. It has since migrated back to the Fatherland and is continuing life on the track with it's latest owner, Matthias Miller, who has continued to improve the car, including the installation of a bespoke 916 flat-six engine that delivers 263 hp at 8000 rpm! He sent me an email today with a link to an article about it recently published in Grand Prix Magazine that is in both German and English in alternating paragraphs.
https://www.grandprix-magazine.de/magazine/911-rr
The original Type 916 engine was apparently developed as a 2-liter 4-cam race motor and fitted in a 910 prototype, but was abandoned in the testing phase due to rule changes that favored development of the 8-cylinder 3.0 liter engine, and later the 12-cylinder for the 917. A group of engineers in Germany used the original specs for the 916 to develop a "916 Reloaded" 2.5 liter version at a "boutique engineering workshop in southern Germany close to Stuttgart," and the 5th iteration of this new engine has been installed in my old '68. Matthias calls it a "911RR" now.
https://911rr.de/the-engine-story/
I would love to have a chance to drive it again with this new powerplant. It was a hoot to drive with a Euro 3.0 of only 204 HP, so an extra 60 HP and 2000 more RPM before redline would make it even more lively, I'm sure!