I bought a pair of Weber 40DFO carbs just to see if it would be possible to use them on a vw engine. The seller listed them as off a fiat but I have not found any evidence of fiat using them. I believe they are off an Opel of some type as that is the only car I have been able to find that use them. I'm familiar with most type of 2 barrel webers but don't remember ever seeing this type. It looks like it will fit a DCNF manifold but appears to be designed more like a DFAV/DFEV except it's got synchronous barrels. Has anyone used these carbs or have any ideas where to look for information about them? Is there a good weber book that has information about them? From my understanding of webers designation it's a down draft carb designed originally for Ferrari or Fiat but that's about all I know about them.