Cast iron? You scared me there, I had to check.....the one we will be getting (from Alpine or elsewhere) is aluminum.
Regarding the stock intake idea, I actually consider the manifold in the kits to be a worse design! It would be great to be able to take advantage of those beaut vertical runners to slam the charge into the engine. (An engineer here in OZ actually developed 350 Chev heads that used that principle for drag boats - the manifold looked like a big spider sitting on the engine!) and maybe even retaining the dual length runner system - but there is one major issue: height. The SC would sit so high you would need a Pro Stock bonnet scoop
Anyway, my Frankenstein project 'Jackadeo' will have body back on chassis soon so I will be able to seriously measure & see - that has a 60mm body lift but will still give us an idea
Cheers for now
Rob