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

I've got some money burning a hole in my pocket, and I'm wondering if it would make any real difference swapping from my current 1 3/4" Headman Hustlers to the 1 7/8" Headman Hustlers. I think my engine is right on the boarder of "needing" 1 7/8" headers, but I'm not sure if I would gain much (if any) with the swap.

My car, incase you are not familiar:

67 Barracuda (about 3250# with me), 408 stroker, 13:1 compression on e85, ported Edelbrocks, 264/268 duration @ 0.05 with 0.621/0.632 lift solid flat tappet, Victor intake, 727 with 8" converter, 4.10 gear, 275/60/r15 Hooiser DR.

Current best 10.1x @ 130mph, but usually runs 10.3x in the summer heat.

I would just hate to spend the time and money on new headers if they don't to squat....or slow the car down.

Thoughts?
Maybe try tuning your collector length first before buying a new set of headers