Big block exhaust is still loud

You need to take the engine down and lower the compression...... Five to one should do it ............ lol.
No Just kidding.
on my 367@ 11/1 the dual 3s are really loud at full-song. I installed the Longest 3-pass dynomax muffs offered in 1999 which quieted it right down. But to be even quieter I installed a GV od and 3.55s, for 65mph =2240rpm.
This set-up came to me from TTI, with an H-pipe. To install the GVod, I had to cut that H out. Afterwards, I notice right off that the engine had lost a very significant amount of off-idle torque, AND the exhaust system was quite a bit louder.
I solved the torque loss by installing a 3.09 low gear trans versus the 2.66 that was in it.
I got used to the louder exhaust around town. If I have company in the car, I just short-shift, or stay off the gas. Those long Dynomaxers are actually pretty good; they've been on the car since 1999.