1 3/4" Headers Verses 1 7/8" on a Healthy 408....Is There a Big Difference??

Since you already have basically a race type header I’m betting you see little to no gain. The exhaust ports on the Edelbrock heads are so screwed up shape wise you are pissing into the wind. I aim for port air speed rather than a flow number and although I always post flow numbers without tubes have tested and played around with different tubing sizes. Invest your money somewhere else.