That's cool.
After some digging I found out:
* The adjustable prop valve is tapped for metric M8 (1 0) which is why the 1/8 not didn't work.
* The short section with the 1/4 in fitting is correct for the input of the factory hold off.
I'm going to either track down the fitting, the original hold off, or flare in a 3/16 fitting.
What a pain in the ***.