http://pitstopusa.com/c-132804-body-...d-plastic.html
Frame it with aluminum strappy things from Lowes using lots of aluminum rivets. Seal it to the mouth of the car and the heat exchangers. My ducting is attached to the radiator mouts on the sides, I made a rail that goes under the rad, all the way accross, and the top side of the radiator is basically wedged between the weld along the top of the core and the inside lip of metal on the inner bumper support. It's worth driving to my house in Lewisville to look at my ducting.