3" exhaust? 2.5" exhaust...??

My 416 stroker is in the 450-500 hp range. Havnt dyno it yet. My dougs headers have a 3" collector. So I thought I would try 3" x pipes with 3" mufflers that drop to 2 1/2" going out to the tailpipes and tips. So far its a great sound and nice tone and seems to breath real nice with the aluminum