not for the racing engine. i do build hudson split manifolds. have done a few for the HET guys. don't know what they put them on.
Yes, took these pictures 40 years ago and scanned the prints but that is a genuine factory 7X exhaust manifold and Twin H with it in the pics. That is the factory headpipe too that went two into one to comply with NASCAR rules that a 6 cyl car could not have two tail pipes past the rear axle. I don't own this setup any more but I used to have it on a '53 SuperWasp brougham with twice pipes and gl*** packs all the way out.
Since it's just an extension that bolts to the standard exhaust manifold, it seems like someone would be recasting it.
I believe the manifold has two separate outlets, and that extension also has two ports through it. So while they are both single castings, they do keep the exhaust from the front three cylinders separated from the back three until it hits that steel pipe collector.
The 7x extension is being recasted. Some gentleman in Al. is doing it. Go over to cl***iccar.com and get on the Hudson board. They will point you in the right direction. Hud