I would cut the bottle neck off also. I did it on my car, then took a ball peened hammer and lightly kept tapping on the new edge until it rolled a bead outward to hold the clamp on. Yes you can use your old IC piping, if you're on a budget or into ghetto mods. You can also go to an auto parts srore and find a radiator hose that you could probably cut down and make it work. They are rated for higher pressures than you'll throw at it. On the other end you will need a reducing coupling, or you can put a 2" hose on that end, then slide your elbow over that hose and clamp both leyers down. Use hairspray to slide these on, and they will setup pretty permanant.