No cutting is required if you are using the alum. radiator by itself. You can use weld on brackets from Northern $$$$$. Or make your own from angled 2" aluminum stock $$. I used some factory holes in the radiator support as my mounting points. I adjusted my brackets according to these holes. Then had the brackets TIG welded ($30 labor fee). Damn I wish I knew how to TIG weld. It would so come in handy. Anyways.
Now if you decide to use their radiator shroud/SPAL puller (2300cfm) fan setup then yes you may need to slightly notch the area where the radiator tanks hit the top support. I needed to notch mine so it would clear the water pump pulley as you can see in the pictures above.
If you didn't ask you would never know I notched the rad. support. I love this setup and love the idea of not having to run a mechanical fan. The other benefit I have is that I live near the ocean and the temperatures are rarely greater than 85*
I use a 180* thermostat in the car and the trigger for the fan kicks in at 185*
I hope to keep it below 200* on the hottest days. I'm also using Redline Water Wetter. Purple Ice from Royal Purple is good too.