I have no way of verifying but the story that I heard was that Ford hired or assigned (depending on your perspective) Holman-Moody to design the manifold.
I presume that means all the flow bench and dyno work on it as well?
They did the tooling also. I don't know who cast them. Some of the Holman-Moody "one-offs" I've seen are said to be rejected prototypes and some of them said Buddy Barr Casting on them with Holman-Moody logos.
The story continues in that it says "the tooling was shipped to Detomaso in Italy". There was no mention of castings or finished manifolds shipped to them.
With any of the "Ford" manifolds I've been associated with it is always presumed that there was a minimum done. That is the case with Offenhauser and Edelbrock castings as well and that number is 100 minimum.
I don't know if there is/was a machining minimum.
The C60A 2x4 Holley Trans-Am manifold that I've got was cast by Buddy Barr, but machined by Offenhauser. It's got OE stampings on it.
I think of those companies like law firms in that they seemed to have been on a "retainer" to Ford.
I'm not sure but Gary Hall was always talking about buying the molds for items like the 10" Campagno wheels. The Hall Pantera manifold looks suspiciously like the Detomaso version but with thicker carb mounting flanges.
I remember a conversation with him where he said "I thickened the flanges and changed the logo".
The part that says Detomaso and Hall Pantera, are what the casting companies call drop in sticks. Those are done separately and just get dropped into the molds before the molten metal gets poured in, so it's pretty easy to change those.
The ONLY Detomaso version I ever saw in person was one that Gary had. He was like a magician in that if you mentioned something he would seemingly pull one out of his sleeve?
I think that the casting quality on his is better then the Detomaso version. I've had three of Hall's. When I saw the Detomaso manifold, it was my impression that it was painted black because the quality of the casting wasn't great. I'd add though that the Holman-Moody one-offs that I've seen were pretty crudely cast as well.
You can actually see in some of the other various manifolds in the casting where they added weld material to the tooling. So maybe there is a connection there? Is that the signature of the artist?
Contrast that to the T/A manifold that I have by comparison and it is so nice it almost looks pressure cast. "A reliable source" said that's because it was made from Ford tooling. Buddy Barr's tooling isn't great either in many cases.
It may in fact be Gary Hall who is the source of this "story" of the Detomaso Weber manifold? I always found him credible. Others opinions vary. I definitely miss him.