I should have just machined the velocity stacks as I originally thought I would in the first place years ago when I started this project. I 3D designed and grew different ones thinking I could do better than old fashioned machining, but they just didn't look like what I wanted when I put them on the carbs. I spent well over 50 hours chasing that approach.
So I went back to "the old way". I ground two steel tools and turned these stacks on my lathe using a compound slide for the inside to follow the shape of the outside cut.
The flanges were made "old school" too as separate parts.