Here's a picture of the fitting that I took out of the block side. The tube slides into the ferrule (marked with the line) which pushes into the adapter (2nd fitting from left).
Strange set up, since the ferrule isn't held in place by a cap nut. The ferrule and hose always floated in the adapter piece, but never leaked. A couple of spines on the ferrule are broken, so it's going to need to be replaced.
I know that the hose isn't 1/8" because I compared to the hose in a VDO replacement kit and the existing hose is larger. Any ideas about what size the hose is and where I can find a replacement fitting?