I've always wanted to try the trick I read in one of David Vizard's books-
welding up the (aluminum) intakes' heat riser entrances, drilling, tapping, and fitting the topside of the passages with heater hose fittings and ball valves (remove the handles for clearance; use only for opening/ shutting, or use a pair of pliers).
Best of both worlds;some heat when needed, but not so intense. And the ability to shut it off without much fuss.
An iron intake would require molten aluminum or some sort of epoxy, but could be done, too, I imagine.
Wish I had access to the pic that accompanied the idea. I think it's in his "How to Build Horsepower" volume 1 book. Mine's in storage.