Header primary tube size

I have 65 mustang with stock shock towers modified and a sbf with a edelbrock victor head puting out 800hp on motor and another 200 of nitrous. Has anyone made there own headers because it is no one out ther making anything larger than a 1 3/4 to a 1 7/8 step becauce I have a set. I heard a 1 7/8 step to a 2 inch might work with a 4 inch collector.