With your cam, I think you may miss your headers, unless you plan to run a turbo in the future. I have run long tube headers on many vehicles, and you don't have to be WOT to feel the difference in the power they make across the entire RPM range. I ran cheap long tubes on an old 99 F150 5.4 and it was crazy the amount of power long tubes made, and I never got it tuned. I am about to add a cam similar to yours in my L9H, and run 1 7/8" ARH long tubes to my stock cat back
Headers definitely make 20-30 ft/lbs more across the range. Power wise they're great, but the ticking noises in the cabin really ruin the comfort of the vehicle and winter is coming, so windows will be up for 6 months.
Plus I'd be comparing a cammed 5.3 with headers to a cammed 6.2 with manifolds and 3.5" exhaust. The cammed 5.3 is still 1 second slower 0-60 than a stock 6.2.