Big block swapping a 1964 barracuda

Dont ya have to cut the firewall corners for headers?
i think, once I get the Engine sitting in there on the mounts and it’s not resting on anything I’ll start measuring for headers. My other idea was to have a single turbo and run about 4lb of boost and have the driver side cross in front and have the exhaust exit above the roof of the car. If you know cleetus McFarlands single turbo c6 corvette i used that car as a example