http://store.spectreperformance.com/...746/2231.0.1.1
Here is the link to the ducting I used for my CAI. I have a ReSpeed radiator support with a 3" OD opening. The ducting runs up to my stock 1st gen air cleaner. I am running a Nikki carb. This stuff is designed for this purpose.
I would stay away from matalic boxes and ducting. It will absorb heat and warm the air on the way in.
There are all kinds of options for down draft carbs, but I have never seen a solution for a side draft.