2" to 3" exhaust... Worth it?

Right now, I can't find the tables and such I used to make my decision.
Once my 360 gets put in the car, it's getting Doug's D453 headers with 2 1/2" pipes and an H pipe. I made these decisions based on what I was able to learn about scavenging and a pack of unladen 'MURICAN swallows air-speed-velocity as they travel in line down the exhaust system and out the pipe. I chose my stuff based on MATH, not how cool it may sound.
Larger diameter pipes than what I have at the output of my small block build; cam, intake, heads, headers et cetera, would not provide as good scavenging and hence intake charge for the next suck-squeeze-bang-blow cycle.