Wow! there's some interesting stuff ... I had always thought that the Vedette V8 was a straight drop-in of the V8-60 (the "little" sv V8 which I think also went into the Ford Pilot).
What mods/alterations did Mathis engineer, then?
And that three-rod/two cylinder arrangement I think I have seen elsewhere.. maybe in an aero engine setting. Not at all sure on that - will do some delving.
Good post!
(later again) Yep ... it was indeed an aero-related engine.
Anzani made an experimental horizontally opposed engine with the 2 pistons-3rod arrangement.
Source - "Aircraft Piston Engines" by Herschel Gibbs (1981). pg 200.
While chasing this up, I found this image on an aero forum thread.
It may not be the same engine, but is very possibly so, I consider, as just about the only "common" Anzanis are the 3 cylinder jobs in either "fan" or (later) "star" arrangement. Fascinating stuff!