Wife says she needs Earplugs!

Hi all. I need your expertise on "droning". It doesn't bother me too much because I love the car, but my wife says she wants earplugs, and she's a car lover, maybe my classic car lover? From 20 to 90mph (WOT) it's fun! No problems there.
I'll try and provide everything I know about the engine rebuild and exhaust system. From about 30 to 40 major droning, up to about 2K RPM, driving around the town and countryside, city, hit the gas it's gone.
Here's what I have.
Car - 1975 Valiant Brougham 2- door
Rebuilt 1975 318 - (only 32,000 miles, but I wanted more than that "smog engine") .30 over with iron 340 heads, not sure if X or J", worked on a little bit" is what I'm told!
The Engine with headers dyno'd at 404HP (at 5,5500), 419 TQ (at 4,100)
Cam - Comp XR280HR-10 (2,2200-6,000rpm)
Manifold - LD4B
Holley - Dominator? Carb 750
Trans - Rebuilt 904 2,500 stall.
Exhaust manifolds - 72-73 340 manifolds
Exhaust - 2 1/2" TTI head pipes, full TTI exhaust with turn downs out the back, Dynomax Turbo mufflers. (The standard TTI kit.)
8 1/4 rear end with 3:55 sure grip.
Back Tires - 245/60/15

Will putting Exhaust Tips out beyond the bumper help or not? Different mufflers? Suggestions please.

Thanks all.