It has clear casting numbers, that don't follow Ford's pattern.
It doesn't have HM or Buddy Bar cast (Buddy Bar usually cast their name on the bottom).
It doesn't seem to have been a 'success' as an experiment as that appears to be the first and last of its line.
I know Kinsler cast some manifolds like that, but I don't think they did so until later, most people associate them with BBC's, but they were pretty ecumenical early on.
Back in the day, its biggest problem, to the aftermarket at least, would have been the 4 58mm webers needed. Pricey, foreign, and not 4v Holleys.
Accept it for what it is, someone tried something new and different.
How did it perform in the Ranchero? What were its performance characteristics? Torquey? Wide-range or narrow band of power? Was it ever on a dyno?