2 1/2 inch exhaust on a 318...

Howdy Folks !
I finally decided what engine I am going to build for my car. A 318 with 4 barrel carb, 360 heads, 4 inch stroke, .030 overbore at least no more than .040 . Hopefully making around the 450-550 hp mark. I would like to know if 2 1/2 inch exhaust would be good for this build. I want to use the TTI headers of course and fab up my own exhaust. So would 2 1/2 be just perfect or a little smaller or go up to 3 inch? Thanks everyone !