Scoggin-Dickey made patterns to cast up their own cast iron Vortec manifold (not a GM part, a Scoggin-Dickey part), but I see it has been discontinued. You might find it by advertising in some roundy-round trade journals. I'd call Scoggin-Dickey just to make sure they don't have 1 left under the counter. I might also call around to some of the local circle track offices and inquire. You never know. It's in my S-D catalog at $169.99 retail, part# 14097499.
http://www.sdparts.com/product/14097...CONTINUED.aspx